Facebook provides a variety of statistics on its Web site that detail the growth

Question

Facebook provides a variety of statistics on its Web site that detail the growth and popularity of the site. on average, 28 percent of 18 to 34 year olds check their Facebook profiles before getting out of bed in the morning suppose this percentage follows a normal distribution with a standard deviation of five percent. 1) Find the probability that the percent of 18 to 34-year-olds who check Facebook before getting out of bed in the manning is at least 30. 2) Find the 95th percentile, and discuss your findings in such a way that your 9th grade brother or sister would be able to understand. Remember, they have to take the EOC exams on material like this.

Explanation / Answer

1. P(X > 30)

= P(z > (30 - 28)/5)

= P(z > 0.4)

= 0.3446

So,

Probability that percent is at least 30 = 0.3446

b) From z table,

P(z < 1.65) = 0.95

Hence,

95th percentile = 28 + 1.65(5) = 36.23

This means that 95% of the times, around 36.23% of 18 to 34 years old checks facebook before going to bed.

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