Aids in decision making by providing comparison of data, explains action that has taken place, justify a claim or assertion, predicts future outcome and estimates un known quantities
Descriptive-comprise those methods concerned with the collection, description, and analysis of a set of data without drawing conclusions or inferences about a larger set.
Inferential-comprise those methods concerned with making predictions or inferences about a larger set of data using only the information gathered from a subset of this larger set.
The word population refers to groups or aggregates of people, animals, objects, materials, happenings or things of any form, this means that there are populations of students, teachers, supervisors, principals, laboratory animals, trees, manufactured articles, birds and many others. If your interest is on few members of the population to represent their characteristics or traits, these members constitute a sample. The measures of the population are called parameters, while those of the sample are called estimates or statistics.
It refers to a characteristic or property whereby the members of the group or set vary or differ from one another. However, a constant refers to a property whereby the members of the group do not differ one another.
Variables can be according to functional relationship which is classified as independent and dependent. If you treat variable y as a function of variable z, then z is your independent variable and y is your dependent variable. This means that the value of y, say academic achievement depends on the value of z.
1. Nominal – this refers to a property of the members of a group defined by an operation which allows making of statements only of equality or difference. For example, individuals can be classified according to thier sex or skin color. Color is an example of nominal variable.
2. Ordinal – it is defined by an operation whereby members of a particular group are ranked. In this operation, we can state that one member is greater or less that the others in a criterion rather than saying that he/it is only equal or different from the others such as what is meant by the nominal variable.
3. Interval – this refers to a property defined by an operation which permits making statement of equality of intervals rather than just statement of sameness of difference and greater than or less than. An interval variable does not have a “true” zero point.; althought for convenience, a zero point may be assigned.
4. Ratio – is defined by the operation which permits making statements of equality of ratios in addition to statements of sameness or difference, greater than or less than and equality or inequality of differences. This means that one level or value may be thought of or said as double, triple or five times another and so on.
Survey Method – questions are asked to obtain information, either through self administered questionnaire or personal interview.
Observation Method – makes possible the recording of behavior but only at the time of occurrence (ex. Traffic count, reactions to a particular stimulus)
3. Experimental method – a method designed for collecting data under controlled conditions. An experiment is an operation where there is actual human interference with the conditions that can affect the variable under study.
4. Use of existing studies – that is census, health statistics, weather reports.
5. Registration method – that is car registration, student registration, hospital admission and ticket sales.
Frequency Distribution is defined as the arrangement of the gathered data by categories plus their corresponding frequencies and class marks or midpoint. It has a class frequency containing the number of observations belonging to a class interval. Its class interval contain a grouping defined by the limits called the lower and the upper limit. Between these limits are called class boundaries.
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Frequency of a Nominal Data Male and Female College students Major in Chemistry 130 TOTAL 107 FEMALE 23 MALE FREQUENCY SEX
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Frequency of Ordinal Data Ex. Frequency distribution of Employee Perception on the Behavior of their Administrators 100 total 31 Strongly unfavorable 22 Unfavorable 14 Slightly unfavorable 12 Slightly favorable 11 favorable 10 Strongly favorable Frequency Perception
Compute the range: R = H – L and the number of classes by K = 1 + 3.322log n where n = number of observations.
Divide the range by 10 to 15 to determine the acceptable size of the interval. Hint: most frequency distribution have odd numbers as the size of the interval. The advantage is that the midpoints of the intervals will be whole number.
Organize the class interval. See to it that the lowest interval begins with a number that is multiple of the interval size.
8. Compute the cumulative distribution for less than and greater than and put them in column cf< and cf>. (you can now interpret the data). cf = cumulative frequency
9. Compute the relative frequency distribution. This can be obtained by
The data can be graphically presented according to their scale or level of measurements.
1. Pie chart or circle graph. The pie chart at the right is the enrollment from elementary to master’s degree of a certain university. The total population is 4350 students
2. Histogram or bar graph- this graphical representation can be used in nominal, ordinal or interval. For nominal bar graph, the bars are far apart rather than connected since the categories are not continuous. For ordinal and interval data, the bars should be joined to emphasize the degree of differences
33.
Given the bar graph of how students rate their library.
A-strongly favorable, 90
B-favorable, 48
C-slightly favorable, 88
D-slightly unfavorable, 48
E-unfavorable, 15
F-strongly unfavorable, 25
34.
The Histogram of Person’s Age with Frequency of Travel 100% 51 total 3.9% 2 27-28 7.8% 4 25-26 7.8% 4 23-24 41.2% 21 21-22 39.2% 20 19-20 RF freq age
Draw its histogram using the frequency in the y axis and midpoints in the x axis.
Draw the line graph or frequency polygon using frequency in the y axis and midpoints in the x axis.
Draw the less than and greater than ogives of the data. Ogives is a cumulation of frequencies by class intervals. Let the y axis be the CF> and x axis be LCB while y axis be CF< and x axis be UCB
Construct the class interval, frequency table, class midpoint(use a whole number midpoint), less than and greater than cumulative frequency, upper and lower boundary and relative frequency.
3. Draw the pie chart and bar graph of the plans of computer science students with respect to attending a seminar. Compute for the Relative frequency of each.
It is an important measure which divides the distribution into one hundred parts. It is called the centile. Other measures similar to the percentile are the quatile and decile. The quartile divides the distribution into four parts while the decile into ten parts.