Bell-Ringer

An airline recorded the number of on-time arrivals for a sample of 100 flights each day. The boxplot below summarizes the recorded data for one year. Based on the boxplot, which of the following statements must be true?

• The range of the number of on-time arrivals is greater than 90.
• The interquartile range of the number of on-time arrivals is 22.
• The number of days that had at least 80 on-time arrivals is greater than the number of days that had at most 76 on-time arrivals.
• The number of days that had from 76 to 80 on-time arrivals is equal to the number of days that had at most 76 on-time arrivals.
• The difference between the median and the lower quartile for the number of on-time arrivals is less than 2.

A tropical storm is classified as major if it has sustained winds greater than 110 miles per hour. Based on data from the past two decades, a meteorologist estimated the following percentages about future storms. 20% of all tropical storms will originate in the Atlantic Ocean, of which 20% will be classified as major. 30% of all tropical storms will originate in the eastern Pacific Ocean, of which 15% will be classified as major. 50% of all tropical storms will originate in the western Pacific Ocean, of which 25% will be classified as major. Based on the meteorologist’s estimates, approximately what is the probability that a future tropical storm will originate in the Pacific Ocean and be classified as major?

• 0.045
• 0.125
• 0.170
• 0.400
• 0.960

Research indicates that the standard deviation of typical human body temperature is 0.4 degree Celsius (C). Which of the following represents the standard deviation of typical human body temperature in degrees Fahrenheit (F), where F = (9/5)C + 32?

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The distribution of weights of female college cross-country runners is approximately normal with mean 122 pounds and standard deviation 8 pounds. Which of the following is closest to the percent of the runners who weigh between 114 pounds and 138 pounds?

• 18%
• 32%
• 68%
• 82%
• 95%

Measurements of water quality were taken from a river downstream from an abandoned chemical dumpsite. Concentrations of a certain chemical were obtained from 9 measurements taken at the surface of the water, 9 measurements taken at mid-depth of the water, and 9 measurements taken at the bottom of the water. What type of study was conducted, and what is the response variable of the study?

• An experiment was conducted, and the response variable is the concentration of the chemical.
• An experiment was conducted, and the response variable is the depth of the water.
• A census was conducted, and the response variable is the depth of the water.
• An observational study was conducted, and the response variable is the concentration of the chemical.
• An observational study was conducted, and the response variable is the depth of the water.