6-2 Real Applications of Normal Distributions 269 IQ Scores. In Exercises 9–12, find the indicated IQ score and round to the nearest whole number. The graphs depict IQ scores of adults, and those scores are normally distributed with a mean of 100 and a standard deviation of 15 (as on the Wechsler IQ test). 9. x 0.9918 10. x 0.1587 11. x 0.9798 12. x 0.9099 Pulse Rates. In Exercises 13–24, use the data in the table below for pulse rates of adult males and females (based on Data Set 1 “Body Data” in Appendix B). Hint: Draw a graph in each case. Pulse Rate (beats per minute) Mean St. Dev. Distribution Males 69.6 11.3 Normal Females 74.0 12.5 Normal 13. Find the probability that a male has a pulse rate less than 60 beats per minute. 14. Find the probability that a female has a pulse rate less than 60 beats per minute. 15. Find the probability that a female has a pulse rate greater than 80 beats per minute. 16. Find the probability that a male has a pulse rate greater than 80 beats per minute. 17. Find the probability that a female has a pulse rate between 70 beats per minute and 90 beats per minute. 18. Find the probability that a male has a pulse rate between 65 beats per minute and 85 beats per minute. 19. Find the probability that a male has a pulse rate between 70 beats per minute and 90 beats per minute. 20. Find the probability that a female has a pulse rate between 60 beats per minute and 70 beats per minute. 21. For males, find P90, which is the pulse rate separating the bottom 90% from the top 10%. 22. For females, find the first quartile Q1, which is the pulse rate separating the bottom 25% from the top 75%. 23. Significance Instead of using 0.05 for identifying significant values, use the criteria that a value x is significantly high if P(x or greater) … 0.01 and a value is significantly low if P(x or less) … 0.01. Find the pulse rates for males that separate significant pulse rates from those that are not significant. Using these criteria, is a male pulse rate of 90 beats per minute significantly high?
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