Biostatistics

Question 1

What is statistics (using information and data)

Answer 1

Statistics is a body of techniques and tools used in the collection, organization, analysis, interpretation and presentation of information that can be stated numerically

It is the collection, presentation, analysis and interpretation of numerical data.

Question 2

Explain the two types of statistics

Answer 2

Descriptive:
Describes the population. Summarizes measurements .
Involves: frequencies, proportions, measures of central tendency, measures of dispersion/variation.
e.g weight of final year medical students

Inferential:
Uses data from a sample to represent the population which the sample came from
e.g weight of final year medical students to represent weight of medical students as a whole

Question 3

Describe types of variables

Answer 3

Quantitative/Numerical:
Are just numbers, whether whole/integers(Discrete) or fractions(continuous). Any thing that can be counted or measured.

Qualitative/Categorical
Describes data that fits into categories.
3 types: Binary, nominal and ordinal

Question 4

meaning of observations

Answer 4

Any subject that serves as the data source e.g people, schools

Question 5

meaning of variables

Answer 5

The thing that can be measured e.g blood pressure

Question 6

meaning of values

Answer 6

The actual result gotten from measuring a variable e.g 130/75mmHg

Question 7

how many people are at least 7 years old? Is this a qualitative or quantitative variable.

Answer 7

Quantitative because the people can be counted. Specifically discrete quantitative.

Question 8

What are measures of central tendency/location

Answer 8

They are tools used to summarize entire quantitative datasets into the most likely value (basically like the average)

Question 9

What are the 3 measures of central tendency

Answer 9

Mean
Median
Mode

Question 10

mean

Answer 10

Simply the arithemetic average
m = ∑x/n

Question 11

Mean for grouped data

Answer 11

Mean = ∑fx /n

Where f = frequency of each group or class
x = mean value of the group
n = number of observations

Question 12

median

Answer 12

The mid value of a series of data
(n + 1)/2
Best for skewed data

Question 13

Mode

Answer 13

Most frequently occurring observation in a series

Question 14

4 common measures of variation/dispersion

Answer 14

Range
Interquartile range
Variance
Standard deviation

Question 15

Range

Answer 15

This is the difference between the largest and smallest values.

For grouped data, it is the difference between the mid-points of the extreme categories

Question 16

Interquartile range

Answer 16

This indicates the spread of the middle 50% of the data

IQR = upper quartile – lowest quartile

Question 17

Upper quartile and lower quartile

Answer 17

Find the median of the entire number series.
Find the median of the lower and upper halves, these two numbers are the lower and upper quartile respectively

Question 18

Variance

Answer 18

variance = (summation(x - m)squared)/(n-1)

Where x = each data point/value
m = mean
n = size of the sample

Question 19

Standard deviation

Answer 19

aka root mean square deviation
It is the square root of the variance

Question 20

Which method of dispersion to use for skewed data

Answer 20

range and IQR

Question 21

Formula for obtaining the standard deivation of grouped data

Answer 21

square root of (∑x² - (∑x)² /n)/(n-1)

Question 22

3 methods of data presentation

Answer 22

Text
Tables/charts
Graphs

Question 23

When can data be used within a text

Answer 23

When there are only two data points being compared

Question 24

Guidelines for drawing a good table

Answer 24

Should be able to stand on its own

Tables should be numbered in Arabic numerals in the order in which they appear (Table 1, 2 etc)

Title should be informative and written above the table

Better to remove grid lines
Use footnotes to explain abbreviations or symbols

Question 25

When can data be used within a table

Answer 25

When the data is more complex

Question 26

When can data be used within a graph

Answer 26

Useful when there are few data points or categories. Also to show trends

Question 27

Guidelines for drawing a good table

Answer 27

Should have an informative title

Title should be written below the graph

Figures should be numbered in Arabic numerals according to the order in which they appear

Legends should be clear (a legend is that colour-coded thing that gives you more information about the graph)

Use strong contrasting colours

Question 28

Guidelines when making a pie chart

Answer 28

Ensure the wedges all add up to 100%
Begin at 12 o’clock position
Go clockwise from largest to smallest
Show no more than 7 wedges
Use distinct colours for wedges

Question 29

What is the major difference between histograms and bar charts

Answer 29

Bar charts are used to represent discrete data, that’s why there are spaces
Histograms are used to represent continuous data

Question 30

Mention 7 types of graphs used for data presentation

Answer 30

Line graph
Stem leaf
Box and whisker plot
Frequency polygon
Histogram
Pie chart
Bar chart

Question 31

What are scales of measurement

Answer 31

Ways in which variables are defined and categorized. It determines the type of statistical analysis that is done.

Question 32

What are the 4 scales of measurement

Answer 32

Nominal
Ordinal
Interval
Ratio

Question 33

Nominal scale

Answer 33

For unordered categorical data
Places people or objects in mutually exclusive categories
Eg. gender

Question 34

Ordinal scale

Answer 34

For ordered categorical data
Ranks objects in order
Eg. Level of education

Question 35

Interval scale

Answer 35

For discrete dataFor discrete data
Units of measurement are equal throughout the full range of the scale but has no ‘true zero’ point
Zero does not represent the absolute lowest value
Addition and subtraction operations can be performed
Eg. Measurement of temperature in degrees

Question 36

Ratio scale

Answer 36

For continuous data
Has a true zero point (No numbers exist below zero)
Can calculate ratios between scale values
All 4 mathematical operations (addition, subtraction, multiplication and division) can be performed
Eg. Height, serum Calcium