General Topics #1
General Topics #2
Statistical Tests #1
Statistical Tests #2
Interpretations
100

What are the goals of statistical analysis?


  • Summarize data
  • Show basic patterns 
  • Interpret patterns
  • Generalize patterns to population
100

What is the first step of hypothesis testing?


  • Formulation of the null hypothesis and the alternative hypothesis


100

 What influences our test results?

  • Sample size

  • Variance (dispersion of sample values)

  • How certain we want to be about the conclusion

100

 If you want to compare two variables for each respondent in the sample, which test should be used?

Paired Sample T-Test

100

What is the impact of a larger sample size?


  • Easier to find statistical significance


200

What is the goal of inferential statistics?


  • Use characteristics of the sample to estimate characteristics of the population

  • In other words, use sample statistics to estimate population parameters


200

A false hypothesis that is not rejected is what Type of Error?

Type II Error

200

When should a One Sample T-test be used?


  • When we want to compare the mean of one sample to a set threshold


200

When testing the relationship between two variables, what tests should be used if our goal is to test difference in means?

  • Paired sample t-test

  • Independent sample t-test

200

Considering a binary “dummy” variable, variables are defined as 0 or 1. What would a 0 variable mean?

  • 0 = condition is false.

  • 1 = condition is true.

300

What are two examples of tests of associations?


  • Correlation (interval and ratio)

  • Proportions (ordinal and nominal) (Chi-Square tests)


300

What is the difference between inferential statistics and descriptive statistics?


  • Inferential statistics: quantities from sample data calculated to make inferences about the population being studied

  • Descriptive statistics: summary measures that describe your sample data


300

When should an Independent Sample T-Test be used?


  • When we want to compare the mean of one variable across two sub-groups in your population


300

When testing the relationship between two variables, what test should be used if our goal is to test associations with frequency distributions?

Bivariate Chi-Square Test

300

What does the R-squared value indicate?


  • What percentage of the variability in Y is explained by X


400

What is the difference between parameter and statistic?


  • Parameter is a number describing the whole population

  • Statistic is a number describing a sample


400


What is the correct interpretation of a p-value that is below alpha?


Rejection of the null hypothesis

400

What test should be used if we want to compare the frequency distribution of a sample variable to a hypothesized population distribution?

Chi-Square Test

400

 

 What does an F-Test tell us?


The F-test of overall significance tells us whether our linear regression model provides a better fit to the data than a model that does not contain independent variables

400

According to this output, when “TR price in $” increases by $1, holding all else constant, what is the predicted increase in MM OJ sales?


+ 114.9

500


What are the two basic properties that we calculate for our sample?


  • Central tendency (mean, median, mode)

  • Dispersion (standard deviation, absolute frequencies, relative frequencies)

500

What are the two steps of the independent t-test?

  • Hypothesis test of equality of variance of 2 samples

  • Hypothesis test of difference of means

500

 What are the assumptions of a Chi-Square Test?


  • The expected counts (Ei) has to be greater than 5 for at least 80% of the cells in the table

  • No cell can have an expected count below 1 

  • These assumptions check if there is enough data for the test to be accurate


500

When does the adjusted R-squared increase?


  • When the new term improves the model more than it would be expected by change

  • But, the adjusted R-squared is always lower than the R-squared


500

 According to this output, when there is a Feature Ad that week, holding all else constant, what is the predicted increase in MM OJ sales?


+ 270.33