*AP exam review for a question you may see on the AP Statistics exam*

Next up, we cover another sample question which can be found from the list of subjects covered by Omninox: AP Statistics. Now this AP exam should not be taken lightly, as accroding to Total Registration, the past 2014 AP Statistics exam had a failure rate of 30.6%. In order to ensure your success, it is important that you practice practice practice! Let's take a look at an example of a typical AP question you may see below.

**The least squares regression line is superimposed on five scatterplots below of a y response versus an x covariate. Which scatterplot shows a good fitting line to the data?**

The answer to this problem is **Figure [A]**. Let's review why the other answers are not the best choices. Figures B and E are essentially the same figure, just flipped. They are not good fits because of the variability of the points above and below the line, so there is no steady trend present.

Figure C does not even come close to fitting the line because of all the points that are amassed to the left side of the graph, which indicates that the data is heavily trending to remain clustered. Figure D follows the general trend of the line however, the missing middle section of points indicate a not so linear fit.

This leaves Figure A, which has the best linear relationship among the points. This is true because the distance between each point and the line is the smallest with this graph. This is the best indication to tell which points have the most linear relationship. Measure the distance between the points and the best fit line. The one that has the most points with the shortest distances is the most linear.

Be sure to look at our other question review posts if you need the help. Other questions that you can look at for review include: AP Chemistry, AP Environmental Science, and AP US History. Well, what are you waiting for get to practicing!

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]]>*The next installment for AP Statistics with a brand new question review*

As we continue with the question reviews for our AP subjects, we come back to an old friend of ours: AP Statistics. In the previous post we had about AP Statistics, we covered the concept of linear regression and linear fitting of data points. This time, the post covers the concept of random sampling and when how exactly is it applicable. As you'll see from the following question, who you sample matters.

**A simple random sample of all teachers in the 9th to 12th grades in New York is taken to better understand teaching practices and increase annual statewide examination scores. The survey results are safely generalizeable to whom?**

Your answer choices are:

- To all teachers in the United States
- To all teachers for the 9th grade in the United States
- To all teachers for the 9th to 12th grades in the United States
- To all teachers in New York
- To all teachers for the 9th to 12th grades in New York

Who you sample matters, as that will affect how you apply the results of your sample. It wouldn't make sense to apply the results of your sample to all the teachers in the United States beucase the teachers you sampled only represent 4 grade levels, so teaching practices from 9th-12th grade are vastly different from K-8. For this same logic, you can also eliminate the choice **To all teachers in New York**, because even though you are narrowing the scope to New York, you still run into the issue of grade levels outside your initial sample scope.

Overall, the results of your sample can only be safely applied to the bounds and demographic that were established in the initial random sample. In this case, since the initial random sample was for high school teachers (9th-12th) in New York, the results are the most representative of the same demographic.

Image Source: http://en.wikipedia.org/wiki/Sampling_%28statistics%29

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