Stats test 1
Jody, a statistics major, grows tomatoes in her spare time. She keeps a record of the weight of each tomato she grows. One tomato is 2 standard deviations heavier than the mean weight. Assume a Normal model is appropriate. What percentile is it in?
97.5
If we want to study the relationship between two quantitative variables such as fat and calorie content of food, what type of graphical display should be made?
A scatterplot
Which of the following best describes a response variable?
A. A response variable is the dependent variable B. The variable that might change in response to a change in the explanatory variable. C. A response variable is the variable you hope to predict or explain. CORRECT> D. All of the above.
Which of the following statement is TRUE about a z-score?
A. A z-score is a measure of how extreme or typical a data value is. B. Z-scores standardize a dataset. C. A z-score tells us how many standard deviations value is from the mean. D. Z-scores have a mean of 0 and a standard deviation of 1. CORRECT: E. All of the above
All outliers have large residuals.
False
The relationship between any two variables can be studied with a scatterplot.
False
Noting a recent study predicting the increase in cell phone costs, a friend remarks that by the time he's a grandfather, no one will be able to afford a cell phone. Explain where his thinking went awry.
He is extrapolating into the future. It is impossible to know if a trend like this will continue so far into the future.
A standardized value is a value found by which of the following?
Subtracting the mean from the value and then dividing the result by the standard deviation of the dataset
Which of the following best describes the explanatory variable?
The explanatory variable explains or predicts changes in the response variable.
Sports announcers love to quote statistics. During football championship games, they particularly love to announce when a record has been broken. They might have a list of all football championship games, along with the scores of each team, total scores for the two teams, margin of victory, passing yards for the quarterbacks, and many more bits of information. Identify the who in this list.
The individual games
Which of the following is not necessarily an outlier?
The maximum value in a dataset
Suppose your statistics professor reports test grades as z-scores, and you got a score of 2.20 on an exam. Write a sentence explaining what that means.
The score was 2.20 standard deviations higher than the mean score in the class.
Which of the following is TRUE about the correlation coefficient?
We should only find correlation between two variables if they are quantitative, the association is straight enough, and there are no outliers.
If our data in a scatterplot is "straight enough" we can model our data with a _____.
linear model.
A variable that is not part of the model but affects the way variables in the model appear to be related is called a(n) _____________.
lurking variable.
The following contingency table shows data from a shipwreck. Here is a two-way table of those aboard this ship, classified according to the class of ticket and whether the ticket holder survived or didn't. To look at the overall distribution of ticket "Class" on this ship, we would find the ____________.
marginal distribution of "Class".
The following contingency table shows data from a shipwreck. Here is a two-way table of those aboard this ship, classified according to the class of ticket and whether the ticket holder survived or didn't. What type of variables are these and why?
Categorical, because each individual fits into specific categories