A is incorrect since the mean is the sum of all numbers divided by the number of data. meaning that if we have 4,5,6,7,8 then the mean is 6 but if we add 32 into our numbers then are mean jumps to 10.333333 (4+5+6+7+8+32)/6. Which 32 is an outlier. As for the median (B) it is correct since the median orders the numbers then you find the middle (we do not use all the numbers). The standard deviation is affected by the outlier since its function is similar to the mean, and the standard deviation is used to indicate which numbers are in fact an outlier. In this case we use all the numbers. As for D it is also correct since the interquartile range is used to find outliers but it divides up the numbers into sections by first finding the median then dividing the first 50% of numbers into two sections by finding the median of that section. As seen the interquartile range uses the median which as we already know from before is not affected by outliers. Once again we do not use all the numbers to find what were looking for.

Thus the answer is A. The mean is not affected by the existence of an outlier is INCORRECT.

May 25th, 2015

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