Module 1

Question 1

How do you get a good sample?

Answer 1

1) Define statistical population clearly and carefully
2) Random sample (representative of the population as possible: each subject has equal chance of being selected and is selected independently of others)
3) Precise
4) Unbiased

Question 2

What is sampling error?

Answer 2

Due to chance alone, the sample is not representative of the true value

Question 3

What is a sample of convenience?

Answer 3

A collection of subjects that are easily available

Question 4

What is a volunteer sample?

Answer 4

Participants volunteer info or participation in the study

Question 5

What is an observational study?

Answer 5

Assignment of the treatments is made by nature

Question 6

What is an experimental study?

Answer 6

The treatments are assigned randomly to individuals by the researchers

Question 7

What is a discrete variable?

Answer 7

Counted and indivisible (can’t have a decimal place of a person)

Question 8

What is a continuous variable?

Answer 8

Measured and can be any value (basically with infinite decimal places)

Question 9

What is a nominal variable?

Answer 9

The variables have no order and moving the categories around doesn’t affect them

Question 10

What is an ordinal variable?

Answer 10

The variables have a meaningful order i.e t-shirt size

Question 11

What is an interval variable?

Answer 11

Has an arbitrary zero (zero doesn’t mean absence of anything)

Question 12

What is a ratio variable?

Answer 12

True/meaningful zero (zero is the absence of something)

Question 13

What is the explanatory variable?

Answer 13

responsible for the change in the response variable (independent)

Question 14

What is the response variable?

Answer 14

Focus of the study, what is being measured (dependent)

Question 15

Frequency distribution

Answer 15

Describes the # of times each value of a variable occurs in a sample
- Bar graph: categorical/discrete data
- Histogram: continuous data

Question 16

Define mean

Answer 16

arithmetic average, very sensitive to extreme values (pulled towards them)

Question 17

Define median

Answer 17

Middle of the data

Question 18

Define mode

Answer 18

Most commonly occurring observation

Question 19

Define range

Answer 19

Max - min, affected by sample size

Question 20

Define residuals

Answer 20

The difference between an observation and a mean
- Sum of the residuals of a sample is always zero
- Residuals can be (+) or (-)
- Sufficiently large sample from a normal distribution will have residuals that are normally distributed and centered on zero

Question 21

Define sum of squares (ss)

Answer 21

Sum of squared deviations from the mean, takes out negative residuals

Question 22

Variance

Answer 22

Expected squared difference between an observation and the mean

Question 23

Standard deviation

Answer 23

Positive square root of the variance, advantage of being in the same unit as the original variable

Question 24

Define estimation

Answer 24

The process of inferring a population parameter from sample data

Question 25

Define uncertainty

Answer 25

The error of an estimate, spread around mean

Question 26

Sampling distribution

Answer 26

The probability distribution of all the values for an estimate that we might have obtained when we sampled the population

Question 27

Increasing the sample size does what to uncertainty?

Answer 27

Decreases the uncertainty

Question 28

Standard error of the mean

Answer 28

Standard deviation of the estimated mean

Question 29

Confidence interval

Answer 29

Range of values that is likely to contain the true population parameter