Week 8

Question 1

population

Answer 1

the broader group of people to whom you intend to generalize the results of your study

Question 2

sample

Answer 2

the group of subjects that actually partcipate in your study

Question 3

sample selection

Answer 3

• random vs non-random sampling
• statistics cannot fix poor methodological choices

Question 4

sample size

Answer 4

• the larger the better, but you need to be practical
• determining sample size is important at the planning stage

Question 5

descriptive analysis

Answer 5

to summarize and describe the characteristics of a dataset
* measures central tendency (mean, median, mode)
* measures of dispersion (range, variance, standard deviation)
* frequency distributions
* percentiles and quartiles

Question 6

correlation analysis

Answer 6

to examine the relationship between two or more variable
* pearson correlation coefficient
* spearman correlation coefficient

Question 7

difference between groups analysis

Answer 7

to compare the means of two or more groups to determine if there are significant differences between them
* t-test (for comparing two groups)
* ANOVA (for comparing more than two groups)

Question 8

categorical/discrete variables

Answer 8

these variables represent categories or distinct groups
* gender
* eye color
* educational level
* country of origin

Question 9

continuous variables

Answer 9

these variables can take on any value within a given range
* height
* weight
* age
* temperature
* income

Question 10

How is central tendency measured in a normal distribution?

Answer 10

mean (arithmetic average)

Question 11

How is variability measured in normal distribution?

Answer 11

standard deviation: numerical indicator of the spread of data
* sigma={sqrt {{sum(x - mean)^{2}}/N}}

Question 12

What percentage of the data are within 1 SD?

Answer 12

68%

Question 13

What are the percent of the data within 2 SD?

Answer 13

95%

Question 14

What percent of data are within 3 SD?

Answer 14

99.7%

Question 15

How is the expected difference between the sample and population means in a normal distribution?

Answer 15

standard error: measures how precise your estimate is when compared to the population of “true” value
* SE = SD / SqrRt( Sample Size)

Question 16

How is central tendency measured in normal distribution?

Answer 16

• median = value in the center of the dataset, the ‘middle’ of a sorted list of numbers
• mode = most frequency occurring data value

Question 17

How is variability measured in non-normal distribution?

Answer 17

• range = high score minus low score
• interquartile = the difference between 75th and 25th percentile

Question 18

Type I Error

Answer 18

• the null hypothesis is rejected when it is true
• probability of type I error = alpha

Question 19

Type II Error

Answer 19

• the null hypothesis is not rejected when it is false
• probability of type II error = beta