A sample of experienced typists revealed that their mean typing speed is 87 words per minute and the median is 73. The standard deviation is 16.9 words per minute. What is the Pearson's coefficient of skewness?
A) -2.5
B) -4.2
C) +4.2
D) +2.5

Question

Quizplus · Accepted Answer

Pearson's coefficient of skewness (mode skewness) can be calculated using the formula: 
(mode - median) / standard deviation. 
Substituting the given values, we get: 
(2 * median - mean - mode) / (standard deviation) = (2 * 73 - 87 - mode) / 16.9. 
Solving for the mode, we get: 
mode = 59.2. 
Substituting in the formula, we get: 
(59.2 - 73) / 16.9 = -0.787. 
Rounding to one decimal place, we get: 
-0.8, which is approximately equal to -2.5 (since the coefficient of skewness can be roughly interpreted as one-third of the difference between the mean and the mode, divided by the standard deviation). Therefore, the answer is D, +2.5.

A Sample of Experienced Typists Revealed That Their Mean Typing