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 0 to 1600. Use technology and the estimated standard deviation to determine the sample size corresponding to a 95% 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 ___. (Type an integer or a fraction.)

A confidence level of 95% requires a minimum sample size of ___

Explanation / Answer

By range of rule of thumb deviation,

Std deviation = R/4 = 1600/4 =400

Std error = 400/rt n

Margin of error = 1.96(std error) = 1.96*400/rtn=100

Or rtn = 7.84

n = 62

Hence answers are:

400 and

62.

Rough std deviation may not give the accurate confidence interval.

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