Normal Probability Distributions

The mean score on a college placement exam is 500 with a standard deviation of 100. Ninety-five percent of the test takers score above what?

• 260
• 336
• 405
• 414

Most graduate schools of business require applicants for admission to take the Graduate Management Admission Council’s GMAT examination. Scores on the GMAT are roughly normally distributed with a mean of 527 and a standard deviation of 112. What is the z-score for this problem?

• z = -0.24107
• z = -0.02312
• z = 0.24107
• z=-0.23128

The average noise level in a restaurant is 30 decibels with a standard deviation of 4 decibels. Ninety-nine percent of the time it is below what value?

• 30 + 1.96(4)
• 30 - 2.576(4)
• 30 + 2.326(4)
• 30 - 2.326(4)

On a TI-84, how do you calculate the p-value?

• Normalcdf(upperbound, lowerbound)
• invNorm(area)
• invNorm(lowerbound, upperbound)
• Normalcdf(lowerbound, upperbound)

The Edwards’s Theater chain has studied its movie customers to determine how much money they spend on concessions. The study revealed that the spending distribution is approximately normally distributed with a mean of $4.11 and a standard deviation of $1.37. What is the z-score for this problem?

• 0.81021
• -0.3456
• -0.81021
• 0.3456

The mean income per household in a certain state is $9,500 with a standard deviation of $1,750. The middle 95% of incomes are between what two values?

• $5,422 and $13,578
• $6,070 and $12,930
• $6,621 and $12,379
• $7,260 and $11,740

On a TI-84, how do you calculate the z-score?

• Normalcdf(lowerbound, upperbound)
• invNorm(area)
• invNorm(lowerbound, upperbound)
• Normalcdf(upperbound, lowerbound)

Jay Olshansky from the University of Chicago was quoted in Chance News as arguing that for the average life expectancy to reach 100, 18% of people would have to live to 120. What standard deviation is he assuming for this statement to make sense?

• 21.7
• 24.4
• 25.2
• 35.0

If 75% of all families spend more than $75 weekly for food, while 15% spend more than $150, what is the mean weekly expenditure and what is the standard deviation?

• =83.33, =12.44
• =56.26, =11.85
• =118.52, =56.26
• =104.39, =43.86

What is the p-value?

• The area between a given interval/z-scores
• The number of standard deviations away from the mean
• The area under the curve
• The number of values in a normal distribution