a student wants to estimate the mean score of all college students for a particu

Question

a student wants to estimate the mean score of all college students for a particular exam. first use the range rule of thumb to make a rough estimate of the standard deviation of those scores. possible scores range from 500 to 1800. use technology and estimated standard deviation to determine the sample size corresponding to a 90% confidence level and a margin of error of 100 points. What isn't quite right with this exercise?

The range rule of thumb estimate for the standard deviation is _____________

A confidence level of 90% requires a minimum sample size of _____________

What isn't quite right with this exercise?

a. these results don't apply to a test that has multiple choice questions.

b. a minimum sample size of 29 it's not feasible to use to estimate the mean test scores

c. a margin of error of 100 points seems too high to provide a good estimate of the mean score

d. the range rule of thumb introduces too much and accuracy for this procedure

Explanation / Answer

The range rule of thumb estimate for the standard deviation is

s R / 4 R = Maximum - Minimum

Where,

s = Standard Deviation R = Range

Thus, standard deviation s=(1800-400)/4=350

The minimum sample size is:

(z(0.90)*sigma/margin of error)^2

=(1.645*350/100)^2

=33.148

or 34

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