Week 9 - Descriptive Statistics

Question 1

Uses for descriptive statistics

Answer 1

1. Descriptive Studies

Question 2

Descriptive studies- what do they do in a set of data

Answer 2

characterize shape, central tendency and variability within a set of data

Question 3

what is the purpose of descriptive studies

Answer 3

describe a sample or population

Question 4

population measures in a descriptive study

Answer 4

parameters

Question 5

Sample measures in a descriptive study

Answer 5

statistic
- statistics are used to estimate population parameters

Question 6

Distribution of data

Answer 6

• readiness for statistical testing

Question 7

what do you need to know for distribution of data

Answer 7

1. central point around which data tends to cluster (average)
   - measure of central tendency
   - “typical value in the set of observations
2. how far from central point all data lies
   - variability
3. examine visual display of scores

Question 8

Frequency of distribution

Answer 8

distribution
- total set of scores for a variable
- N=total # of scores in distribution
- summarize data with frequency of distribution; a table of rank ordered scores and frequency of each

Question 9

How can you graph frequency of distribution

Answer 9

1. histogram
2. line plot
3. stem and leaf plot
4. distribution shape: skewed right/positively skewed or skewed left/negatively skewed

Question 10

Central tendency: mean

Answer 10

• arithmetic average
• can be influenced by extreme values
• sample mean: x̄
• population mean:μ

Question 11

Central tendency: median

Answer 11

• middle score of distribution
  1. put data points in order select middle data point

Question 12

Central Tendency mode

Answer 12

• score that occurs most frequently in distribution
• blue
• most for categories

Question 13

Measure of variability

Answer 13

1. Range: difference between highest and lowest values of distribution
2. percentiles: describe scores position within distribution
   - convert scores into comparative scores
3. quartiles: divide distribution into 4 quarters

Question 14

Box and whisker plots

Answer 14

• box: interquartile range (between 1st and 3rd quartile)
• whiskers: range of scores
• horizontal line: 50th percentile = median

Question 15

Coefficient of variation

Answer 15

• ratio of standard deviation to mean
• expressed as %
• can compare between different types of measures, between different distribution