1. Suppose the time spent by UNCC students studying for math exams per week is normally distributed with a mean of 65 minutes and a standard deviation of 13 minutes. a. What is the probability that a randomly chosen student spends between 60 and 90 minutes per week studying for math exams? b. If 50 UNCC students are randomly selected, approximately how many are expected to study fewer than 20 minutes per week?

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I'm pretty sure that the answer for part A can be found by using the normalCDF function on my TI-84 Calculator. Plugging in 60 as the Lower Bound, 90 as the Upper Bound, 65 for the mean, and 13 for the Standard Deviation results in a probability of 0.6225.

However, I tried the same for part B, plugging in 0 as the Lower Bound, 20 as the Upper Bound, 65 for the mean, and 13 for the Standard Deviation. This resulted in a probability of 0.0002683, which doesn't seem right to me. I would greatly appreciate it if someone could double check my reasoning and if wrong, explain which formula I should use to get the correct answer for part B.

1. Suppose the time spent by UNCC students studying for math exams per week is normally
distributed with a mean of 65 minutes and a standard deviation of 13 minutes.
a. What is the probability that a randomly chosen student spends between 60 and 90
minutes per week studying for math exams?
b. If 50 UNCC students are randomly selected, approximately how many are expected to
study fewer than 20 minutes per week?
Transcribed Image Text:1. Suppose the time spent by UNCC students studying for math exams per week is normally distributed with a mean of 65 minutes and a standard deviation of 13 minutes. a. What is the probability that a randomly chosen student spends between 60 and 90 minutes per week studying for math exams? b. If 50 UNCC students are randomly selected, approximately how many are expected to study fewer than 20 minutes per week?
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