After entering the test scores from her Statistics class of 33 students, the instructor calculated the mean, median, IQR and standard deviation of the tes scores. Upon checking, she discovered that she had entered the top score as 85 , but it should have been 95 . a) When she corrects this score, how will the mean and median be affected? b) What effect will correcting the error have on the IQR and the standard deviation? a) Determine how the mean will be affected. Select the correct choice below and, if necessary, fill in the answer box within your choice. A. The mean will increase by \( \square \) points. (Round to two decimal places as needed.) B. The mean will decrease by \( \square \) points. (Round to two decimal places as needed.) C. The mean will not change. D. It is impossible to determine how the mean will change.
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When that top score goes from 85 to 95, the sum of all the test scores will increase, thus raising the mean. To find out how many points it increases, you can use the formula for the mean, which is the total sum of scores divided by the number of students. In this case, with an increase of 10 points (the difference between 95 and 85) across 33 students, the mean will increase by \( \frac{10}{33} \), which is approximately \( 0.30 \) points. The median, on the other hand, is determined by the middle score in a sorted list. Since the score of 95 will likely change the placement of students below the median, you may find the median also increases, especially if the median was around or below 85. If the median score doesn’t include the top score, it may not change, but if it’s at or near that value, it could boost up, shifting the median score by at least a point or two, depending on the distribution of the other scores. So, in conclusion: A. The mean will increase by \( 0.30 \) points.