STAT 202: Inferential Statistics and Data Analysis Exam
Variable A is independent of Variable B - answers✔✔Which of the following is the appropriate
null hypothesis (H0) for a chi-squared test of independence?
Having lower levels of stress causes you to sleep longer at night - answers✔✔Data was collected
that contains the hours per night a person sleeps and their stress level on a scale of 1 to 10. In
conducting a correlation test between these two variables, we find that the correlation is -0.74,
with a p-value of 0.01. Which of the following statements is true?
True - answers✔✔A linear regression model was conducted to predict the rent for an
apartment by using square feet (size) of the apartment as a predictor variable. The data that
was used to build the model contained apartments that ranged from 750 to 2000 square feet. I
can use this model to predict the rent for an apartment that is 1900 square feet.
Goodness Of Fit - answers✔✔When comparing actual data to hypothetical
proportions/frequencies, I am running a Chi-Squared Test Of:
True - answers✔✔Linear regression assumes all variables are independent of each other.
Yes - answers✔✔A linear regression model is conducted and the coefficient for the variable is
+2 with a 95% confidence interval of [-1, +5]. Is this variable significant at an alpha if 0.05?
25% - answers✔✔A chi-squared test is being used to determine whether the purchase
frequency of 4 different types of cell phones differ. A sample of 1000 cell phone purchases was
recorded. As a hypothetical frequency, I assume that the purchase frequency is uniformly
distributed (i.e. there is no difference). What expected proportions should I use for each of the 4
cell phone types?
, It causes variables to become insignificant in the regression model even if they are significantly
correlated with the dependent variable - answers✔✔Which of the following statements about
multi-collinearity is true?
independence of errors (no auto correlation) (?) - answers✔✔A gym used a linear regression
model to estimate monthly membership numbers over the last 5 years using time as an
independent variable. After completing the model, the plotted their errors/residuals and
noticed that the dependent variable (membership) correlated with past membership values.
Which assumption of linear regression does this violate?
linear regression (?) - answers✔✔A store has collected monthly sales data for the past 10 years.
Their data has a trend and seasonal component. Which method should be used to analyze this
data?
Trend - general movement over all years
Cycle - repetitive up and down movement around the trend that covers several years
Seasonal - repetitive cyclical pattern within a year
Irregular - a random disturbance that follows no apparent pattern - answers✔✔components of
time series
R^2 does not decrease when you add predictors, while Adjusted R^2 may increase, stay the
same, or decrease.
Adjusted R^2 tests different independent variables against the model while R^2 does not. -
answers✔✔Differences between R^2 and Adjusted R^2
Variable A is independent of Variable B - answers✔✔Which of the following is the appropriate
null hypothesis (H0) for a chi-squared test of independence?
Having lower levels of stress causes you to sleep longer at night - answers✔✔Data was collected
that contains the hours per night a person sleeps and their stress level on a scale of 1 to 10. In
conducting a correlation test between these two variables, we find that the correlation is -0.74,
with a p-value of 0.01. Which of the following statements is true?
True - answers✔✔A linear regression model was conducted to predict the rent for an
apartment by using square feet (size) of the apartment as a predictor variable. The data that
was used to build the model contained apartments that ranged from 750 to 2000 square feet. I
can use this model to predict the rent for an apartment that is 1900 square feet.
Goodness Of Fit - answers✔✔When comparing actual data to hypothetical
proportions/frequencies, I am running a Chi-Squared Test Of:
True - answers✔✔Linear regression assumes all variables are independent of each other.
Yes - answers✔✔A linear regression model is conducted and the coefficient for the variable is
+2 with a 95% confidence interval of [-1, +5]. Is this variable significant at an alpha if 0.05?
25% - answers✔✔A chi-squared test is being used to determine whether the purchase
frequency of 4 different types of cell phones differ. A sample of 1000 cell phone purchases was
recorded. As a hypothetical frequency, I assume that the purchase frequency is uniformly
distributed (i.e. there is no difference). What expected proportions should I use for each of the 4
cell phone types?
, It causes variables to become insignificant in the regression model even if they are significantly
correlated with the dependent variable - answers✔✔Which of the following statements about
multi-collinearity is true?
independence of errors (no auto correlation) (?) - answers✔✔A gym used a linear regression
model to estimate monthly membership numbers over the last 5 years using time as an
independent variable. After completing the model, the plotted their errors/residuals and
noticed that the dependent variable (membership) correlated with past membership values.
Which assumption of linear regression does this violate?
linear regression (?) - answers✔✔A store has collected monthly sales data for the past 10 years.
Their data has a trend and seasonal component. Which method should be used to analyze this
data?
Trend - general movement over all years
Cycle - repetitive up and down movement around the trend that covers several years
Seasonal - repetitive cyclical pattern within a year
Irregular - a random disturbance that follows no apparent pattern - answers✔✔components of
time series
R^2 does not decrease when you add predictors, while Adjusted R^2 may increase, stay the
same, or decrease.
Adjusted R^2 tests different independent variables against the model while R^2 does not. -
answers✔✔Differences between R^2 and Adjusted R^2
