Stats 101 Short Answers

Question 1

How do we Plot One Numeric Variable?

Answer 1

Dot/box plots.

Question 2

How do we Plot One Categorical Variable?

Answer 2

Frequency table, bar chart.

Question 3

How do we Plot Two Numeric Variables?

Answer 3

Scatter plots.

Question 4

How do we Plot One Numeric and One Categorical Variable?

Answer 4

Side by side plots with same scale.

Question 5

How do we Plot Two Categorical Variables?

Answer 5

Two way table of counts, side by side bar charts.

Question 6

What is a Cross-Section Observational Study?

Answer 6

Group of individuals at a point in time.

Question 7

What is a Longitudinal Observational Study?

Answer 7

Group of individuals over a long period of time.

Question 8

What does the Standard Error of the Sampling Mean Measure?

Answer 8

The average distance between a sample mean and the population mean.

Question 9

How do we Calculate Confidence Intervals?

Answer 9

Estimate ± t x se(estimate).

Question 10

What are the Symbols for a Single Mean as a Parameter and an Estimate?

Answer 10

Parameter = μ
Estimate = x̄

Question 11

What are the Symbols for a Single Proportion as a Parameter and an Estimate?

Answer 11

Parameter = p
Estimate = p̂

Question 12

How do you Build a Bootstrap Confidence Interval?

Answer 12

From original sample randomly sample until resamples match original sample size, calculate an estimate, do many resamples with many estimates, use central 95% to find upper and lower limits.

Question 13

How do we Produce a Confidence Interval by Hand?

Answer 13

State the parameter, state the estimate, write down formula, use the given standard error, use the given t-multiplier, calculate confidence limits, interpret in plain English.

Question 14

What Happens to the T-Multiplier when the Level of Confidence Increases?

Answer 14

It also increases.

Question 15

What are 3 Effects of Increasing Confidence Level?

Answer 15

Increased t-multiplier, increased width of confidence interval, estimate statement is less precise.

Question 16

What are 4 Effects of Increasing Sample Size?

Answer 16

Decrease standard error of estimate, decrease t-multiplier in terms of means, decrease width of confidence interval, estimate statement is more precise.

Question 17

What can we Infer from a Random Assignment of Units to Groups?

Answer 17

Experiment-to-causation.

Question 18

What can we Infer from a Random Sampling of Units?

Answer 18

Sample-to-population.

Question 19

How do you Perform a Hypothesis Test by Hand?

Answer 19

State parameter, state null hypothesis, state alternative hypothesis, state estimate, calculate test statistic, estimate p-value, interpret p-value, calculate confidence interval, interpret in plain English, conclude.

Question 20

What is the Only Form of the Null Hypothesis?

Answer 20

Ho: parameter = hypothesised value.

Question 21

What is the 2-Sided Form of the Alternative Hypothesis?

Answer 21

H1: Parameter ≠ hypothesised value.

Question 22

What are the 2 1-Sided Forms of the Alternative Hypothesis?

Answer 22

H1: Parameter < hypothesised value.
H1: Parameter > hypothesised value.

Question 23

What Does a Higher Test Statistic Mean?

Answer 23

Greater evidence against the null hypothesis.

Question 24

What Does a Lower P-Value Mean?

Answer 24

Stronger evidence against the null hypothesis.

Question 25

What is the Critical P-Value?

Answer 25

0.05.