1) This exercise uses the normal probability density function and requires the use of either technology or a table of values of the standard normal distribution.
Repeated measurements of a student's IQ yield a mean of 115, with a standard deviation of 10. What is the probability that the student has an IQ between 112 and 118? (Round your answer to four decimal places.)
2) This exercise uses the normal probability density function and requires the use of either technology or a table of values of the standard normal distribution.
The cash operating expenses of the regional phone companies during the first half of 1994 were distributed about a mean of $29.87 per access line per month, with a standard deviation of $2.25. Company A's operating expenses were $28.00 per access line per month. Assuming a normal distribution of operating expenses, estimate the percentage of regional phone companies whose operating expenses were closer to the mean than the operating expenses of Company A were to the mean. (Round your answer to two decimal places.)
3) This exercise uses the normal probability density function and requires the use of either technology or a table of values of the standard normal distribution.
The cash operating expenses of the regional phone companies during the first half of 1994 were distributed about a mean of $29.87 per access line per month, with a standard deviation of $2.95. Company N's operating expenses were $36.61 per access line per month in the first half of 1994. Estimate the percentage of regional phone companies whose operating expenses were higher than those of Company N. (Round your answer to two decimal places.)