Module 6

Question 1

categorical variables: descriptive statistics

Answer 1

• report frequency and relative frequencies as percentages

Question 2

categorical variables: graphic displays

Answer 2

• bar chart for nominal
• histograms for ordinal variables (use bar chart if the histogram is not available)

Question 3

continuous variables: descriptive statistics

Answer 3

• measures of central location : mean median mode
• measures of spread: SD, statistical range, epidemiological range, Q1 Q3 IQR

Question 4

continuous variables: graphic display

Answer 4

-histogram
-stem and leaf
-box plot with tukey fences

Question 5

what graphic display is used to assess the normality of the distribution?

Answer 5

• visually evaluate the distribution using: HISTOGRAM with the overlay of the normal distribution
  stem and leaf plot

Question 6

what test is used to perform a statistical test of normality?

Answer 6

shapiro wilk test

Question 7

what graphic display is used to assess for the presence of outliers?

Answer 7

box-and-whisker plot with tukey fences

Question 8

when can parametric test be used? (3)

Answer 8

• interval or ratio level data AND
• data are normally distributed AND
• there are not outliers

Question 9

when can nonparametric procedure be used? (3)

Answer 9

-nominal and ordinal data OR
-interval/ratio data that are not normally distributed OR
- interval/ratio level data wit outliers

Question 10

what are cross tabulations?

Answer 10

used to examine relationships between nominal and ordinal variables with a small number of categories

Question 11

commonly used test for cross tabulations

Answer 11

• chi-square (most commonly used)
• fisher exact test (only for 2 dichotomous variables
• mcnemar test (only for dependent measures)

Question 12

p-value if the null hypothesis is accepted

Answer 12

p-value ≥.05

Question 13

p-value if the null hypothesis is rejected and the alternative hypothesis is accepted

Answer 13

p-value <.05

Question 14

chi-square

Answer 14

can be used to test for a relationship between 2 nominal variables

Question 15

fisher exact test

Answer 15

• both variables are dichotomous variables (2x2 table)
• the sample size is small
• a cell in the table has an expected frequency of <5
• can only be used for independent observations

Question 16

McNemar test

Answer 16

-used when you have paired or dependent observations
-replicate measures of the same person or thing
- two methods of measuring the same variable in the same person
- can only be used when both variables are dichotomous (2x2 table)

Question 17

pearson’s correlation coefficient

Answer 17

-if both variables are normally normally distributed
-without outliers
-measured at the interval or ratio level

Question 18

spearman correlation coefficient

Answer 18

-if at least one of the variables is measured at the ordinal level or is measured at the interval or ratio level
- is not normally distributed or has outliers

Question 19

strength of the correlation

Answer 19

• determined by the absolute value of r (e.g. it doesnt matter if r is positive or negative)
• <0.3 weak relationship
• 0.3-0.5 moderate relationship
• > 0.5 strong relationship
• the strength of the correlation is a measure of the ‘effect size’