Methods Of Summarising Data Flashcards
Before one can display data graphically what must happen
one has to organize the data in the form of tables, which summarize data into compact and readily comprehensible form as frequency distribution.
Importance of frequency distribution table and define it
Frequency distribution table is a table showing number of observations at different values of the variable.
•The purpose is to display meaningful pattern. It can be used for all types of data discrete or continuous.
In tabular presentations which of these statements are true
The categories must be mutually exclusive and mutually exhaustive. each disease must belong to a category and only one category of the table. True or false
- Avoid open ended intervals. True or false
- Limit the number of classes to between 10‑20. True or false
- Classes could be of equal or unequal widths. True or false
True
True
True
True
When is a category mutually exclusive and mutually exhaustive
Mutually exhaustive meaning at all cost one of the numbers in the samples must occur
Mutually exclusive: if you have 2 events only one can occur
Both can’t occur at the same time
Frequency polygons,
•the frequency is plotted at the midpoints of the intervals and for
•intervals of unequal widths, the heights on the y‑axis must be re‑adjusted.
True or false
True
For qualitative data, i.e. data not characterized by numeric quantity such as sex of patient, diseases seen at out‑patient department, summarization is by counting the numbers of observations in various categories and expressing them as proportion or percentage
True or false
True
MEAN
•Sum of the individual items divided by the total number of items. It is amenable to mathematical manipulation, but is easily affected by extreme observations.
True or false
True
the case of data classified into intervals, the frequencies are multiplied by the mid‑class point. Because it is not known exactly where the frequencies are located within the classes. •Class mid point is obtained by adding the two class limits and dividing by two True or false
True
It is the middle‑most ranked observation. It is less influenced by extreme values, however, it is not easily amenable to mathematical manipulation.
•It is the best measure of central tendency in case of skewed distributed data.
True or false for median
True
GEOMETRIC MEAN
•It is a useful summary statistic in antibody assay and microbacterial counts and for skewed data. It is defined as the Nth root of the product of N observations.
•It is not used if any of the observations is negative.
True or false
True
information about the variation within groups will provide useful additional statistics which could help to rate the strength of each group.
True or false
True
•RANGE:
•It is the simplest measure of spread
•defined as the difference between the highest and the lowest observations.
•It tends to increase as the number of observations increases.
•It is not easily used for statistical inference.
•It only uses 2 of the observations and neglects all the information regarding variation
True or false
True
The semi inter‑quartile range is also a measure of variation and unlike the range, it does not vary with the number of observations. However, it is not a satisfactory measure of variation for small series of observations unless the number is divisible by 4.
True or false
True
Coefficient of variation It is a dimensionless statistic.
•CV = standard deviation / mean
True or false
True
The following data represent the number of correct responses made to the examination in statistics by 50 medical students in the Medical School selected systematically from the list of all students in the School.
72 72 93 70 59 78 74 65 73 80
57 67 72 57 83 76 74 56 68 67
74 76 79 72 61 72 73 76 67 49
71 53 67 65 100 83 69 61 72 68
65 51 75 68 75 66 77 61 64 74 a. Prepare the frequency distribution table and the frequency histogram for this data set. b. Compute the sample mean , sample median , sample range R, and sample variance . c. Does the data set represent a sample or a population? If it is a sample, describe the population from which it has been drawn.
Solve
Okay
