5. A Nielsen study indicates that mobile subscribers between 18 and 24 years of age spend a substantial amount of time watching video on their devices, reporting a mean of 325 minutes per month. Assume that the amount of time watching video on a mobile device per month is normally distributed and that the standard deviation is 50 minutes. a. What is the probability that an 18- to 24-year-old mobile subscriber spends less than 250 minutes watching video on his or her mobile device per month? b. What is the probability that an 18- to 24-year-old mobile subscriber spends between 250 minutes and 400 minutes watching video on his or her mobile device per month? c. What is the probability that an 18- to 24-year-old mobile subscriber spends more than 400 minutes watching video on his or her mobile device per month? d. 1% of all 18- to 24-year-old mobile subscribers will spend less than how many minutes watching video on his or her mobile device per month?
Continuous Probability Distributions
Probability distributions are of two types, which are continuous probability distributions and discrete probability distributions. A continuous probability distribution contains an infinite number of values. For example, if time is infinite: you could count from 0 to a trillion seconds, billion seconds, so on indefinitely. A discrete probability distribution consists of only a countable set of possible values.
Normal Distribution
Suppose we had to design a bathroom weighing scale, how would we decide what should be the range of the weighing machine? Would we take the highest recorded human weight in history and use that as the upper limit for our weighing scale? This may not be a great idea as the sensitivity of the scale would get reduced if the range is too large. At the same time, if we keep the upper limit too low, it may not be usable for a large percentage of the population!
5. A Nielsen study indicates that mobile subscribers between 18 and 24 years of age spend a substantial
amount of time watching video on their devices, reporting a mean of 325 minutes per month. Assume
that the amount of time watching video on a mobile device per month is
the standard deviation is 50 minutes.
a. What is the probability that an 18- to 24-year-old mobile subscriber spends less than 250 minutes
watching video on his or her mobile device per month?
b. What is the probability that an 18- to 24-year-old mobile subscriber spends between 250 minutes and
400 minutes watching video on his or her mobile device per month?
c. What is the probability that an 18- to 24-year-old mobile subscriber spends more than 400 minutes
watching video on his or her mobile device per month?
d. 1% of all 18- to 24-year-old mobile subscribers will spend less than how many minutes watching video
on his or her mobile device per month?
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