AP Statistics : AP Statistics

Study concepts, example questions & explanations for AP Statistics

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Example Questions

Example Question #1 : How To Find Outliers

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

Min: 

Q1: 

Med: 

Q3: 

Max: 

Which of the following is true regarding outliers? 

Possible Answers:

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 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 is only one outlier in this entire 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 are no outliers in this 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  and  formulas, we can determine that both the minimum and maximum values of the data set are outliers.

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

Which values in the above data set are outliers?

Possible Answers:

no outliers

Correct answer:

Explanation:

Step 1: Recall the definition of an outlier as any value in a data set that is greater than  or less than .

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

. Then, find the median, which is  . Next, Find the median of data below , which is  . Do the same for the data above  to get . By finding the medians of the lower and upper halves of the data, you are able to find the value,  that is greater than 25% of the data and , the value greater than 75% of the data. 

Step 3: . No values less than 64.

. In the data set, 105 > 104, so it is an outlier.  

Example Question #12 : Bivariate Data

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:

Correct answer:

Explanation:

An outlier is any data point that falls  above the 3rd quartile and below the first quartile.  The inter-quartile range is  and .  The lower bound would be  and the upper bound would be .  The only possible answer outside of this range is .

Example Question #1 : How To Create Residual Plots

On a residual plot, the -axis displays the __________ and the -axis displays __________.

Possible Answers:

residuals; the independent variable

 residuals; the  residuals

dependent variable; residuals

independent variable;

independent variable; the dependent variable

Correct answer:

independent variable;

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 #12 : Bivariate Data

       

   

Possible Answers:

    

     

Correct answer:

     

Explanation:

     

Example Question #1 : How To Do Logarithmic Transformations

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

Graphic residual analysis 6

Possible Answers:

Nothing, the data set is already linear

take the log of the dependent variable

multiply the independent variable by

multiply the dependent variable by a constant k.

Add  to the y-value of each data point

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:

Bar chart

Z-score

Histogram

Bell curve

Scatterplot

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 #2 : Graphing Data

Based on the scatter plot below, is there a correlation between the  and  variables? If so, describe the correlation.

Question_11

Possible Answers:

No; there is no correlation

Yes; negative exponential relationship

Yes; negative linear relationship

Yes; positive linear 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 #3 : Graphing Data

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

,  , ,  ,  

Scattertot

Possible Answers:

, ,

, ,

,  ,  

, ,

,  ,  

Correct answer:

, ,

Explanation:

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

Example Question #2 : Graphing Data

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

Possible Answers:

Correct answer:

Explanation:

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

minimum: 

maximum: 

So,

maximum - minimum = 

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