AP Statistics : AP Statistics

Study concepts, example questions & explanations for AP Statistics

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Example Questions

Example Question #271 : Ap Statistics

Use the following five number summary to answer the question below:

Min: \displaystyle 4

Q1: \displaystyle 60

Med: \displaystyle 68

Q3: \displaystyle 76

Max: \displaystyle 185

Which of the following is true regarding outliers? 

Possible Answers:

There are no outliers in this data set.

There are no outliers in the upper side of the data set, but there is at least one outlier on the lower side of the data set.

There is at least one outlier in the lower side of the data set and at least one outlier in the upper side of the data set. 

There are no outliers in the lower side of the data set, but there is at least one outlier on the upper side of the data set.

There is only one outlier in this entire data set.

Correct answer:

There is at least one outlier in the lower side of the data set and at least one outlier in the upper side of the data set. 

Explanation:

Using the \displaystyle Q1-1.5*IQR and \displaystyle Q3+1.5*IQR formulas, we can determine that both the minimum and maximum values of the data set are outliers.

\displaystyle Q1-1.5*IQR

\displaystyle 60-1.5*16=36

\displaystyle Q3+1.5*IQR

\displaystyle 76+1.5*16=100

This allows us to determine that there is at least one outlier in the upper side of the data set and at least one outlier in the lower side of the data set. Without any more information, we are not able to determine the exact number of outliers in the entire data set.

Example Question #1 : How To Find Outliers

\displaystyle 87, 75, 79, 87, 88, 85, 89, 90, 75, 79, 105

Which values in the above data set are outliers?

Possible Answers:

\displaystyle 105

no outliers

\displaystyle 75, 75

\displaystyle 105, 75, 75

\displaystyle 90, 105

Correct answer:

\displaystyle 105

Explanation:

Step 1: Recall the definition of an outlier as any value in a data set that is greater than \displaystyle Q3+1.5*IQR or less than \displaystyle Q1-1.5*IQR.

Step 2: Calculate the IQR, which is the third quartile minus the first quartile, or \displaystyle Q3-Q1. To find \displaystyle Q1 and \displaystyle Q3, first write the data in ascending order.

\displaystyle 75, 75, 79, 79, 85, 87, 87, 88, 89, 90, 105. Then, find the median, which is  \displaystyle 87. Next, Find the median of data below \displaystyle 87, which is \displaystyle Q1 = 79 . Do the same for the data above \displaystyle 87 to get \displaystyle Q3 = 89. By finding the medians of the lower and upper halves of the data, you are able to find the value, \displaystyle Q1 that is greater than 25% of the data and \displaystyle Q3, the value greater than 75% of the data. 

Step 3: \displaystyle Q1-1.5*IQR = 79 - 1.5*10 = 64. No values less than 64.

\displaystyle Q3+1.5*IQR= 89 + 1.5*10 = 104. In the data set, 105 > 104, so it is an outlier.  

Example Question #3 : How To Find Outliers

A certain distribution has a 1st quartile of 8 and a 3rd quartile of 16. Which of the following data points would be considered an outlier?

Possible Answers:

\displaystyle 27

\displaystyle 30

\displaystyle 7

\displaystyle 12

\displaystyle 2

Correct answer:

\displaystyle 30

Explanation:

An outlier is any data point that falls \displaystyle 1.5\ast IQR above the 3rd quartile and below the first quartile.  The inter-quartile range is \displaystyle 16-8=8 and \displaystyle 1.5\ast8=12.  The lower bound would be \displaystyle 8-12=-4 and the upper bound would be \displaystyle 16+12=28.  The only possible answer outside of this range is \displaystyle 30.

Example Question #271 : Ap Statistics

On a residual plot, the \displaystyle x-axis displays the __________ and the \displaystyle y-axis displays __________.

Possible Answers:

independent variable; the dependent variable

residuals; the independent variable

independent variable; \displaystyle y - \hat{y}

dependent variable; residuals

\displaystyle x residuals; the \displaystyle y residuals

Correct answer:

independent variable; \displaystyle y - \hat{y}

Explanation:

A residual plot shows the difference between the actual and expected value, or residual. This goes on the y-axis. The plot shows these residuals in relation to the independent variable.

Example Question #71 : Data

       

   

Possible Answers:

    

     

Correct answer:

     

Explanation:

     

Example Question #72 : Data

What transformation should be done to the data set, with its residual shown below, to linearize the data?

Graphic residual analysis 6

Possible Answers:

multiply the independent variable by \displaystyle 2

multiply the dependent variable by a constant k.

Add \displaystyle 65 to the y-value of each data point

take the log of the dependent variable

Nothing, the data set is already linear

Correct answer:

take the log of the dependent variable

Explanation:

Taking the log of a data set whose residual is nonrandom is effective in increasing the correleation coefficient and results in a more linear relationship.

Example Question #1 : How To Interpret Dotplots

A basketball coach wants to determine if a player's height can be used to predict the number of points that player scores in a season.  Before using a statistical test to determine the precise relationship of the variables, the coach wants a visual of the data to see if there is likely to be a relationship.  Which of the following should the coach create?

Possible Answers:

Z-score

Histogram

Bell curve

Scatterplot

Bar chart

Correct answer:

Scatterplot

Explanation:

A scatterplot is a diagram that shows the values of two variables and provides a general illustration of the relationship between them.

Example Question #271 : Ap Statistics

Based on the scatter plot below, is there a correlation between the \displaystyle \small x and \displaystyle \small y variables? If so, describe the correlation.

Question_11

Possible Answers:

Yes; negative linear relationship

Yes; positive linear relationship

No; there is no correlation

Yes; negative exponential relationship

Correct answer:

Yes; negative linear relationship

Explanation:

The data points follow an overall linear trend, as opposed to being randomly distributed. Though there are a few outliers, there is a general relationship between the two variables.

A line could accurately predict the trend of the data points, suggesting there is a linear correlation. Since the y-values decrease as the x-values increase, the correlation must be negative. We can see that a line connecting the upper-most and lower-most points would have a negative slope.

An exponential relationship would be curved, rather than straight.

Example Question #71 : Data

Order the correlation coefficients to fit the order of the following graphs (two coefficients will not be used)

\displaystyle -1,  \displaystyle -0.7, \displaystyle 0,  \displaystyle 0.3,  \displaystyle 0.8\displaystyle 1

Scattertot

Possible Answers:

\displaystyle 0,  \displaystyle 1,  \displaystyle -0.7\displaystyle 0.3

\displaystyle 0, \displaystyle -1, \displaystyle 0.8\displaystyle -0.7

\displaystyle 0,  \displaystyle 1,  \displaystyle -0.7\displaystyle 0.8

\displaystyle 0.3, \displaystyle -0.7, \displaystyle 1\displaystyle -1

\displaystyle 0, \displaystyle -1, \displaystyle 0.3\displaystyle -0.7

Correct answer:

\displaystyle 0, \displaystyle -1, \displaystyle 0.8\displaystyle -0.7

Explanation:

The first graph is random scatter, no correlation, the second is perfect linear, corellation \displaystyle -1, the last two have fairly strong positive and negative corellations, the student should know that a corellation of \displaystyle 0.3 is much weaker than them

Example Question #1 : Graphing Data

Find the range of the data in the stem-and-leaf plot.

\displaystyle \left.\begin{matrix} 1\\ 2\\ 3\\ 4\\ \end{matrix}\right|\begin{matrix} 12345\\ 00012569\\ 01337\\ 138\\ \end{matrix}

Possible Answers:

\displaystyle 37

\displaystyle 20

\displaystyle 11

\displaystyle 59

Correct answer:

\displaystyle 37

Explanation:

To find the range, subtract the minimum value from the maximum value

minimum: \displaystyle 11

maximum: \displaystyle 48

So,

maximum - minimum = \displaystyle 48-11 = 37

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