A 40-question multiple-choice statistics exam is graded as number correct minus 1/4 the number incorrect, so...
A 40-question multiple-choice statistics exam is graded as number correct minus 1/4 the number incorrect, so scores can range from -10 to +40. Suppose the standard deviation for one class's results is reported to be -3.14. What is the proper conclusion?
A) More students received negative scores than positive scores.
B) At least half the class received negative scores.
C) An error was made in calculating the standard deviation.
D)Some students must have received negative scores.
E) Some Students must have received positive scores.
Homework Answers
Answer is C) An error was made in calculating the standard deviation.
Standard deviation can't be negative because it is distance from the mean.
The sample standard deviation formula is
we know that the standard deviation is a square root of variance and variance is always positive.
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