This document discusses statistical concepts for summarizing data, including:
1. Prevalence refers to existing cases of a condition in a population at a given time, while incidence is the number of new cases over a period.
2. Location measures like mode, median, and mean summarize the central tendency of data. The mean uses all data values, while the median is not affected by outliers.
3. Spread measures like range, interquartile range, and standard deviation describe how dispersed data values are. The standard deviation is the most common measure of spread.
4. Choosing the appropriate summary measure depends on the type of variable (nominal, ordinal, or continuous) and whether the data is ske
Lecture on Introduction to Descriptive Statistics - Part 1 and Part 2. These slides were presented during a lecture at the Colombo Institute of Research and Psychology.
This slideshow explains the important measures of central tendency in statistics. It deals with Mean, mode and median; its characteristics, its computation, merits and demerits. This slideshow will be useful to students, teachers and managers.
Frequency distribution, central tendency, measures of dispersionDhwani Shah
The presentation explains the theory of what is Frequency distribution, central tendency, measures of dispersion. It also has numericals on how to find CT for grouped and ungrouped data.
Lecture on Introduction to Descriptive Statistics - Part 1 and Part 2. These slides were presented during a lecture at the Colombo Institute of Research and Psychology.
This slideshow explains the important measures of central tendency in statistics. It deals with Mean, mode and median; its characteristics, its computation, merits and demerits. This slideshow will be useful to students, teachers and managers.
Frequency distribution, central tendency, measures of dispersionDhwani Shah
The presentation explains the theory of what is Frequency distribution, central tendency, measures of dispersion. It also has numericals on how to find CT for grouped and ungrouped data.
These annotated slides will help you interpret an OR or RR in clinical terms. Please download these slides and view them in PowerPoint so you can view the annotations describing each slide.
TESTS OF SIGNIFICANCE
Deals with techniques to know how far the difference between the estimates of different samples is due to sampling variation.
Standard error (S.E) of Mean = S.D/√n
Standard error (S.E) of Proportion = √pq/n
Tests of significance:
Can be broadly classified into 2 types
1. Parametric tests (or) standard tests of hypothesis
2. Non – Parametric tests (or) distribution free-test of hypothesis
PARAMETRIC TESTS:
Parametric test is a statistical test that makes assumptions about the parameters of the population distribution(s) from which ones data is drawn.
When to use parametric test???
Subjects should be randomly selected
Data should be normally distributed
Homogeneity of variances
The important parametric tests are:
1) z-test
2) t-test
3) ANOVA
4) Pearson correlation coefficient
Z - Test:
This is a most frequently used test in research studies.
Z - test is based on the normal probability distribution and is used for judging the significance of several statistical measures, particularly the mean.
Z - test is used when sample size greater than 30. Test of significance for large samples
Z = observation – mean
SD
Prerequisites to apply z- test
Sample must be selected randomly
Data must be quantitative
Variable is assumed to follow normal distribution in the population
Sample size must be greater than 30. if SD of population is known, z test can be applied even sample size is less than 30
2) t- Test
• In case of samples less than 30 the Z value will not follow the normal distribution
• Hence Z test will not give the correct level of significance
• In such cases students t test is used
• It was given by “WS Gossett” whose pen name was student. So, it is also called as Student test.
There are two types of student t Test
1. Unpaired t test
2. Paired t test
Criteria for applying t- test
1. Random samples
2. Quantitative data
3. Variable normally distributed
4. Sample size less than 30
Unpaired test:
• Applied to unpaired data of independent observation made on individuals of 2 separate groups or samples drawn from the population.
• To test if the difference between the 2 means is real or it can be due to sampling variability.
Paired t - test:
• It is applied to paired data of observation from one sample only (observation before and after taking a drug)
Examples:
1. Pulse rate before and after exertion
2. Plaque scores before and after using oral hygiene aid
3) ANOVA ( Analysis of Variance):
• Investigations may not always be confined to comparison of 2 samples only
• In such cases where more than 2 samples are used ANOVA can be used.
• Also when measurements are influenced by several factors playing their role e.g. factors affecting retention of a denture, ANOVA can be used.
Indications:
To compare more than two sample means
Types:
1. one-way ANIVA
2. Two-way ANOVA
3. Multi-way ANOVA
Pearson’s correlation
Descriptive statistics are used to describe the basic features of the data in a study. They provide simple summaries about the sample and the measures. Together with simple graphics analysis, they form the basis of virtually every quantitative analysis of data.
ANALYSIS ANDINTERPRETATION OF DATA Analysis and Interpr.docxcullenrjzsme
ANALYSIS AND
INTERPRETATION
OF DATA
Analysis and Interpretation of Data
https://my.visme.co/render/1454658672/www.erau.edu
Slide 1 Transcript
In a qualitative design, the information gathered and studied often is nominal or narrative in form. Finding trends, patterns, and relationships is discovered inductively and upon
reflection. Some describe this as an intuitive process. In Module 4, qualitative research designs were explained along with the process of how information gained shape the inquiry as it
progresses. For the most part, qualitative designs do not use numerical data, unless a mixed approach is adopted. So, in this module the focus is on how numerical data collected in either
a qualitative mixed design or a quantitative research design are evaluated. In quantitative studies, typically there is a hypothesis or particular research question. Measures used to assess
the value of the hypothesis involve numerical data, usually organized in sets and analyzed using various statistical approaches. Which statistical applications are appropriate for the data of
interest will be the focus for this module.
Data and Statistics
Match the data with an
appropriate statistic
Approaches based on data
characteristics
Collected for single or multiple
groups
Involve continuous or discrete
variables
Data are nominal, ordinal,
interval, or ratio
Normal or non-normal distribution
Statistics serve two
functions
Descriptive: Describe what
data look like
Inferential: Use samples
to estimate population
characteristics
Slide 3 Transcript
There are, of course, far too many statistical concepts to consider than time allows for us here. So, we will limit ourselves to just a few basic ones and a brief overview of the more
common applications in use. It is vitally important to select the proper statistical tool for analysis, otherwise, interpretation of the data is incomplete or inaccurate. Since different
statistics are suitable for different kinds of data, we can begin sorting out which approach to use by considering four characteristics:
1. Have data been collected for a single group or multiple groups
2. Do the data involve continuous or discrete variables
3. Are the data nominal, ordinal, interval, or ratio, and
4. Do the data represent a normal or non-normal distribution.
We will address each of these approaches in the slides that follow. Statistics can serve two main functions – one is to describe what the data look like, which is called descriptive statistics.
The other is known as inferential statistics which typically uses a small sample to estimate characteristics of the larger population. Let’s begin with descriptive statistics and the measures
of central tendency.
Descriptive Statistics and Central Measures
Descriptive statistics
organize and present data
Mode
The number occurring most
frequently; nominal data
Quickest or rough estimate
Most typical value
Measures of central
tendenc.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdfJim Jacob Roy
Cardiac conduction defects can occur due to various causes.
Atrioventricular conduction blocks ( AV blocks ) are classified into 3 types.
This document describes the acute management of AV block.
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
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RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
4. Learning objectives
1. Explain what prevalence and incidence are.
2. Explain what a summary measure of location is, and
show that you understand the meaning of, and the
difference between, the mode, the median and the
mean.
3. Be able to calculate the mode, median and mean for a
set of values.
4. Explain what a percentile is, and calculate any given
percentile value.
5. Explain what a summary measure of spread is, and show
that you understand the difference between, and can
calculate, the range, the interquartile range and the
standard deviation.
5.
6. Numbers, percentages and proportions
• When you present the results of an investigation, you
will almost certainly need to give the numbers of the
subjects involved; and perhaps also provide values for
percentages.
• It is usually categorical data that are summarized with
a value for percentage or proportion.
7. Prevalence and the incidence rate
When suitable we can also summarize data by providing a
value for the prevalence or the incidence rate of some
condition.
• Prevalence of a disease is the number of existing cases
in some population at a given time. In practice, the period
prevalence is more often used.
• i.e. the prevalence of Breast Cancer in women in a place
in 2010 was 3.1%. The prevalence figure will include
existing cases, i.e. those who contracted the disease
before 2010, and still had it, as well as those first
getting the disease in 2010.
8.
9. Incidence or inception rate of a disease is the number
of new cases occurring per 1000, or per 10 000, of the
population , during a given period, usually 12 months.
10. Summary measures of location
A summary measure of location is a value around which
most of the data values tend to congregate or center.
There are three measures of location
• Mode
• Median
• Mean
11. Mode
• The mode is that category or value in the data that has
the highest frequency (i.e. occurs the most often). In this
sense, the mode is a measure of common-ness or
typical-ness.
• The mode is not particularly useful with metric
continuous data where no two values may be the same.
The other deficiency of this measure is that there may be
more than one mode in a set of data.
Patients Number of inhaler use in last 24 hours
A 5
B 12
C 10
12. Median
• If we arrange the data in ascending order of size, the
median is the middlemost number in the set. Thus, half
of the values will be equal to or less than the
median value, and half equal to or above it. The
median is thus a measure of central-ness.
• i.e. Age (in ascending order of years), for 5 individuals:
30 31 32 33 35. The middle value is 32, so the median
age for these 5 people is 32 years.
13. • Another way of determining the value of the median, If you
have “n” values arranged in ascending order, then: the
median = 1 / 2(n + 1)th value.
• i.e., if the ages of six people are: 30 31 32 33 35 36, then n
= 6, therefore:
• 1 / 2(n + 1) = 1 / 2 × (6 + 1) = 1 / 2 × 7 = 3.5
• Then, median is the 3.5th value. That is, it is the value half
way between the 3rd value of 32, and the 4th value of 33,
or 32.5 years, which is the same result as before.
• An advantage of the median is that it is not much affected
by skewness in the distribution, or by the presence of
outliers. However, it discards a lot of information, because it
ignores most of the values, apart from those in the center
of the distribution.
14. Mean
• The mean, or the arithmetic mean to give it its full name,
is more commonly known as the average.
• One advantage of the mean over the median is that it
uses all of the information in the data set.
• However, it is affected by skewness in the distribution,
and by the presence of outliers in the data.
• This may, on occasion, produce a mean that is not very
representative of the general mass of the data.
• Moreover, it cannot be used with ordinal data.
15. Percentiles
• A percentile (or a centile) is a measure used in statistics
indicating the value below which a given percentage of
observations in a group of observations fall. For example,
the 20th percentile is the value (or score) below which 20
percent of the observations may be found.
• Percentiles are the values which divide an ordered set of
data into 100 equal-sized groups.
• Notice that this makes the median the 50th percentile,
since it divides the data values into two equal halves, 50
per cent above the median and 50 per cent below.
16. Choosing the most appropriate measure
• How do you choose the most appropriate measure of
location for some given set of data?
• The main thing to remember is that the mean cannot be
used with ordinal data (because they are not real
numbers), and that the median can be used for both
ordinal and metric data (particularly when the latter is
skewed).
Type of variable Summary measure of location
Mode Median Mean
Nominal Yes Yes No
Ordinal Yes No No
Metric Discrete Yes Yes, if distribution Yes
Metric Continuous No Is markedly skewed Yes
Choosing an appropriate measure of location
17. Summary measures of spread
As well as a summary measure of location, a summary
measure of spread or dispersion can also be very useful.
There are three main measures in common use
• Range
• Interquartile range
• Standard Deviation
18. Range
• The range is the distance from the smallest value to the
largest. The range is not affected by skewness, but is
sensitive to the addition or removal of an outlier value. i.e,
the range of the 30 birth weights is (2.86 – 4.49 kg).
• The range is best written like this, rather than as the
single-valued difference, i.e. as 1.6 kg, in this example,
which is much less informative.
• The range can sometimes be misleading when there are
extremely high or low values.
19. The interquartile range (iqr)
• One solution to the problem of the sensitivity of the range to
extreme value (outliers) is to remove a quarter (25 %) of the
values off both ends of the distribution (which removes any
troublesome outliers), and then measure the range of the
remaining values. This distance is called the interquartile
range, or iqr.
• The interquartile range is not affected either by outliers or
skewness, but it does not use all of the information in the
data set since it ignores the bottom and top quarter of
values.
20.
21. Standard Deviation
The Standard Deviation is a measure of how spread out
numbers are.
Its symbol is σ (the Greek letter sigma)
The formula is easy: it is the square root of the Variance.
So now you ask, "What is the Variance?“
Variance
The Variance is defined as:
The average of the squared differences from the Mean.
22. You and your friends have just measured the heights of
your dogs (in millimeters):
The heights (at the shoulders) are: 600mm, 470mm,
170mm, 430mm and 300mm.
Find out the Mean, the Variance, and the Standard
Deviation.
Your first step is to find the Mean
Mean =
600 + 470 +
170 + 430 +
300 =
1970
= 394
5 5
23. So the mean (average) height is 394 mm. Let's plot
this on the chart:
24. To calculate the Variance, take each difference, square it,
and then average the result:
Now we calculate each dog's difference from the Mean:
So, the Variance is 21,704.
25. And the Standard Deviation is just the square root of
Variance, so:
Standard Deviation: σ = √21,704 = 147.32... = 147
(to the nearest mm)
And the good thing about the Standard Deviation is that
it is useful. Now we can show which heights are within
one Standard Deviation (147mm) of the Mean
So, using the Standard Deviation we have a "standard"
way of knowing what is normal, and what is extra large
or extra small.
26. • The smaller this mean distance is, the narrower the
spread of values must be, and vice versa.
• This idea is the basis for what is known as the standard
deviation, or SD
27.
28. Type of variable Summary measure of location
Range Interquartile range Standard deviation
Nominal No No No
Ordinal Yes Yes No
Metric Yes Yes, if skewed Yes
Choosing an appropriate measure of spread