The ROC curve is a graph that plots the true positive rate against the false positive rate for different cut-points of a diagnostic test. It shows the relationship between sensitivity and specificity as the cut-point is varied. Moving the cut-point to require a higher test result for a positive diagnosis improves sensitivity but reduces specificity, and vice versa. The closer the ROC curve follows the top left corner, the more accurate the test. The area under the curve provides a measure of test accuracy. The ROC curve was originally developed in WWII for analyzing radar images but is now widely used for evaluating medical diagnostic tests.
VALIDITY AND RELIABLITY OF A SCREENING TEST seminar 2.pptxShaliniPattanayak
A presentation shedding some insight into the tricky concepts of validity and reliability of any screening test, used in day-to-day lives, using easy and understandable language.
Running head HYPOTHESIS TEST 1HYPOTHESIS TESTING.docxcowinhelen
Running head: HYPOTHESIS TEST 1
HYPOTHESIS TESTING 7
Project Phase 3 – Scenario 2
Author Note
This paper is being submitted on
Explain the 8 Steps in hypothesis testing.
1. State null hypothesis- this is the opposite of the expected results, the importance of stating the null hypothesis is because according to Karl Popper’s principle or Falsifiabilty, it not possible to exclusively confirm a hypothesis but it is possible to conclusively negate a hypothesis.
2. Alternative hypothesis- this is indication of what the experiment expects. It is stated as not all equal, because despite the fact that it is possible to have not all equal variables it is only one of the many chances. For instance, when comparing effect of infectious disease of the colour of urine the alternative hypothesis can state that disease 1 results in tinting of the colour of urine to yellow but disease 2, 3… and normal un-infected persons do not differ in the colour of urine.
3. Set α- this is the level of significance. This is the probability or chance of committing the ‘grievous’ error type one denoted by α
There are two types of errors;
Reality
decision
H0 is correct
H0 in incorrect
Accept H0
OK
Type 2 error which is the β equal to possibility of type 2 error.
H0 rejected
Type 1 error
α=possibility of type 1 error
OK
4. Data collection- it’s important to use valid data collection techniques possibly for this case use observational or experimental methods
5. Stating and calculating the statistics for the study- this are the statistic values tested which include the mean, population, sample proportion and the difference in mean and sample proportions.
mean
61.82
median
61.50
mode
69.50
Mid-range
58
range
41
variance
79.64
Standard deviation
8.3
6. Decide on the test to be used- there are basically two types of tests; one tailed and two tailed. The decision is reached depending on the spread of error; two tailed is used when error spread is on two extremes side while one tailed test is used when error is spread on one side in the distribution.
7. Create accept and reject regions- a critical F value is established, you can establish the study F value from the statistical tables it is also called the Fα. It represent the minimum value for the study test statistics which determine which values should be rejected. With the value of F you locate it in the F distribution which form the location for boundary for acceptance and rejection.
8. Standardize the test statistics to draw a conclusion- using step 5 and 6 you can make some inference on the study, but to make more specific conclusion computation of z-test will help decide on the whether to reject or accept the hypothesis. In such cases p-value lower then α, then null hypothesis H0 is conclusively negated and therefore should accept the alternative hypothesis HA.
In testing a hypothesis using the above eight steps I prefer using critical value.
This method include the coming up with the unlik ...
The ppt is a short description about how to ascertain the validity, ie; sensitivity and specificity of a screening test as well as their predictive powers. you can also find the technique to ascertain the best possible screening test through the help of an ROC curve...
VALIDITY AND RELIABLITY OF A SCREENING TEST seminar 2.pptxShaliniPattanayak
A presentation shedding some insight into the tricky concepts of validity and reliability of any screening test, used in day-to-day lives, using easy and understandable language.
Running head HYPOTHESIS TEST 1HYPOTHESIS TESTING.docxcowinhelen
Running head: HYPOTHESIS TEST 1
HYPOTHESIS TESTING 7
Project Phase 3 – Scenario 2
Author Note
This paper is being submitted on
Explain the 8 Steps in hypothesis testing.
1. State null hypothesis- this is the opposite of the expected results, the importance of stating the null hypothesis is because according to Karl Popper’s principle or Falsifiabilty, it not possible to exclusively confirm a hypothesis but it is possible to conclusively negate a hypothesis.
2. Alternative hypothesis- this is indication of what the experiment expects. It is stated as not all equal, because despite the fact that it is possible to have not all equal variables it is only one of the many chances. For instance, when comparing effect of infectious disease of the colour of urine the alternative hypothesis can state that disease 1 results in tinting of the colour of urine to yellow but disease 2, 3… and normal un-infected persons do not differ in the colour of urine.
3. Set α- this is the level of significance. This is the probability or chance of committing the ‘grievous’ error type one denoted by α
There are two types of errors;
Reality
decision
H0 is correct
H0 in incorrect
Accept H0
OK
Type 2 error which is the β equal to possibility of type 2 error.
H0 rejected
Type 1 error
α=possibility of type 1 error
OK
4. Data collection- it’s important to use valid data collection techniques possibly for this case use observational or experimental methods
5. Stating and calculating the statistics for the study- this are the statistic values tested which include the mean, population, sample proportion and the difference in mean and sample proportions.
mean
61.82
median
61.50
mode
69.50
Mid-range
58
range
41
variance
79.64
Standard deviation
8.3
6. Decide on the test to be used- there are basically two types of tests; one tailed and two tailed. The decision is reached depending on the spread of error; two tailed is used when error spread is on two extremes side while one tailed test is used when error is spread on one side in the distribution.
7. Create accept and reject regions- a critical F value is established, you can establish the study F value from the statistical tables it is also called the Fα. It represent the minimum value for the study test statistics which determine which values should be rejected. With the value of F you locate it in the F distribution which form the location for boundary for acceptance and rejection.
8. Standardize the test statistics to draw a conclusion- using step 5 and 6 you can make some inference on the study, but to make more specific conclusion computation of z-test will help decide on the whether to reject or accept the hypothesis. In such cases p-value lower then α, then null hypothesis H0 is conclusively negated and therefore should accept the alternative hypothesis HA.
In testing a hypothesis using the above eight steps I prefer using critical value.
This method include the coming up with the unlik ...
The ppt is a short description about how to ascertain the validity, ie; sensitivity and specificity of a screening test as well as their predictive powers. you can also find the technique to ascertain the best possible screening test through the help of an ROC curve...
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Ethnobotany and Ethnopharmacology:
Ethnobotany in herbal drug evaluation,
Impact of Ethnobotany in traditional medicine,
New development in herbals,
Bio-prospecting tools for drug discovery,
Role of Ethnopharmacology in drug evaluation,
Reverse Pharmacology.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
How to Split Bills in the Odoo 17 POS ModuleCeline George
Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
TESDA TM1 REVIEWER FOR NATIONAL ASSESSMENT WRITTEN AND ORAL QUESTIONS WITH A...
ch 18 roc.doc
1. 18
ROC Curve
(Receiver Operating Characteristic curve)
The accuracy of a medical diagnostic tool depends on its
specificity, the probability that it classifies a normal person as
normal, and its sensitivity, the probability that it classifies a
diseased person as diseased. The receiver operating
characteristic (ROC) curve of such a tool where ‘sensitivity’
plotted against ‘1-specificity’ as the threshold defining
"normal" versus "diseased" ranges over all possible values.
(Jason C. Hsu, Peihua Qiu, Lin Yee Hin, Donald O. Mutti, Karla
Zadnik. Multiple comparisons with the best ROC curve.
Available at: http://projecteuclid.org)
The sensitivity and specificity of a diagnostic test depends on
more than just the "quality" of the test--they also depend on
the definition of what constitutes an abnormal test. Look at the
idealized graph below
showing the number of patients with and without a disease
arranged according to the value of a diagnostic test. This
2. Biostatistics-153
distributions overlap--the test (like most) does not distinguish
normal from disease with 100% accuracy.
The area of overlap indicates where the test cannot distinguish
normal from disease. In practice, we choose a cutpoint
(indicated by the vertical black line) above which we consider
the test to be abnormal and below which we consider the test
to be normal. The position of the cutpoint will determine the
number of true positive, true negatives, false positives and false
negatives. We may wish to use different cutpoints for different
clinical situations if we wish to minimize one of the erroneous
types of test results.
Example: Patients with Suspected Hypothyroidism
Consider the following data on patients with suspected
hypothyroidism reported by Goldstein and Mushlin (J Gen
Intern Med 1987;2:20-24.). They measured T4 and TSH values in
ambulatory patients with suspected hypothyroidism and used
the TSH values as a gold standard for determining which
patients were truly hypothyroid.
T4 value Hypothyroid Euthyroid
5 or less 18 1
5.1 - 7 7 17
7.1 - 9 4 36
9 or more 3 39
Totals: 32 93
Notice that these authors found considerable overlap in T4
values among the hypothyroid and euthyroid patients
Suppose that patients with T4 values of 5 or less are
considered to be hypothyroid. The data display then
reduces to:
3. Biostatistics-154
T4 value Hypothyroid Euthyroid
5 or less 18 1
> 5 14 92
Totals: 32 93
You should be able to verify that the sensivity is 0.56 and the
specificity is 0.99.
Now, suppose we decide to make the definition of
hypothyroidism less stringent and now consider patients
with T4 values of 7 or less to be hypothyroid. The data
display will now look like this:
T4 value Hypothyroid Euthyroid
7 or less 25 18
> 7 7 75
Totals: 32 93
You should be able to verify that the sensivity is 0.78 and the
specificity is 0.81.
Lets move the cut point for hypothyroidism one more time:
T4 value Hypothyroid Euthyroid
< 9 29 54
9 or more 3 39
Totals: 32 93
You should be able to verify that the sensivity is 0.91 and the
specificity is 0.42.
Now, take the sensitivity and specificity values above and put
them into a table:
Cutpoint Sensitivity Specificity
5 0.56 0.99
7 0.78 0.81
9 0.91 0.42
4. Biostatistics-155
Notice that you can improve the sensitivity by moving to
cutpoint to a higher T4 value--that is, you can make the
criterion for a positive test less strict. You can improve the
specificity by moving the cutpoint to a lower T4 value--that is,
you can make the criterion for a positive test more strict. Thus,
there is a transaction between sensitivity and specificity. You
can change the definition of a positive test to improve one but
the other will decline.
Plotting and Intrepretating an ROC Curve
The operating characteristics (above table) can be reformulated
slightly as follows
Cutpoint True positive rates
(Sensitivity)
False positive rates
(1-Specificity)
5 0.56 0.01
7 0.78 0.19
9 0.91 0.58
Data of the above table can be plotted graphically as shown
below
5. Biostatistics-156
This type of graph is called a Receiver Operating
Characteristic curve (or ROC curve.) It is a plot of the true
positive rate against the false positive rate for the different
possible cutpoints of a diagnostic test.
An ROC curve demonstrates several things:
1. It shows the transaction between sensitivity and
specificity (any increase in sensitivity will be
accompanied by a decrease in specificity).
2. The closer the curve follows the left-hand border and
then the top border of the ROC space, the more
accurate the test.
3. The closer the curve comes to the 45-degree diagonal
of the ROC space, the less accurate the test.
4. The area under the curve is a measure of text accuracy.
A final note of historical interest
6. Biostatistics-157
You may be wondering where the name "Reciever Operating
Characteristic" came from. ROC analysis is part of a field called
"Signal Dectection Therory" developed during World War II for
the analysis of radar images. Radar operators had to decide
whether a blip on the screen represented an enemy target, a
friendly ship, or just noise. Signal detection theory measures
the ability of radar receiver operators to make these important
distinctions. Their ability to do so was called the Receiver
Operating Characteristics. It was not until the 1970's that signal
detection theory was recognized as useful for interpreting
medical test results.
[Q: write short note on: ROC curve. (BSMMU, MD Radiology,
January, 2009)]