# Confidence Intervals

Dr Patton is a professor of English. Recently he counted the number of misspelled words in a group of student essay. For his class of 40 students, the mean number of misspelled words was 6.05 and the standard deviation 2.44 per essay. Construct a 95% confidence interval for the mean number of misspelled words in the population of student essays.

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#### Solution Preview

Solution. Given a sample mean xbar=6.05, sample standard deviation s=2.44 and sample size n=40. For a 95% confidence level, z=1.96.

So, a 95% ...

#### Solution Summary

The expert constructs a 95% confidence interval for the mean number of misspelled words in the population.

$2.19