A college statistics class conducted a survey of how students spend their money.

Question

A college statistics class conducted a survey of how students spend their money. They asked 25 students to estimate how much money they typically spend each week on fast food. They determined that the mean amount spent on fast food is $31.52 with a standard deviation of $21.60. Later they realized that a value entered as $3 should have been $30. They recalculate the mean and standard deviation. The mean is now $32.60. Which of the following is true about the standard deviation? The standard deviation will increase, because we have increased the value of a data point. The standard deviation will stay the same, because the standard deviation is not affected by a change in a single measurement. The standard deviation will decrease, because this change moved a data point closer to the mean.

Explanation / Answer

Since, the data wrongly entered as 3 would be 30, it surely affects standard deviation, because, the value is close to mean 31.52, which decreases the variability of the data set. As individual value becomes close to mean, the standard deviation (which is difference of each value from mean) will decrease. Option c)

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