Probabilities and Statistics  Assignment 2
Questions:
1.(5 marks) A press release from Gartner indicates that 79.0% of all smartphones sold in the second quarter of 2013 were Android, and 14.2% of all smartphones sold in the second quarter of 2013 were iOS:
http://www.gartner.com/newsroom/id/2573415
If 30 smartphones sold in the second quarter of 2013 are randomly selected:
 Find the probability that less than 5 are iOS.
 Find the probability that 20 or 21 are Android.
 Find the probability that at least 22 are Android.
 Find the probability that exactly 3 have an operating system that is not iOS and not Android.
2.(5 marks) Recent YouTube statistics show that an average of 100 hours of video are uploaded to YouTube every minute:
http://www.youtube.com/yt/press/statistics.html
 Determine the probability that 99 hours of video are uploaded to YouTube in the next minute.
 Determine the probability that 100 or 101 or 102 hours are uploaded to YouTube in the next minute.
 Determine the probability that less than 99 hours of video are uploaded to YouTube in the next minute.
 Determine the probability that more than 102 hours of video are uploaded to YouTube in the next minute.
3.(5 marks) A recent post by eMarketer.com indicates that the amount of time that US adults spend on nonvoice mobile activities per day is normally distributed with a mean of 2.35 hours and a standard deviation of 0.89 hours.
http://www.emarketer.com/Article/DigitalSetSurpassTVTimeSpentwithUSMedia/1010096
If a US adult is randomly selected:
 Determine the probability that he/she spends between 1.50 and 3.00 hours per day per day on nonvoice mobile activities.
 Determine the probability that he/she spends less than 1.00 hour per day per day on nonvoice mobile activities.
 Determine the probability that he/she spends more than 2.50 hours per day per day on nonvoice mobile activities.
 Determine the probability that he/she spends between 4.00 and 5.00 hours per day per day on nonvoice mobile activities.
4.(5 marks) Determine the probability of flipping 60 or more tails out of 100 flips of a fair coin using a:
 Binomial distribution.
 Poisson distribution with µ=50.
 Normal distribution with µ=50 and σ =5.

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Solution: probabilities assignment 2