Smartphones:A poll agency reports that

75%

of teenagers aged

12

-

17

own smartphones. A random sample of

234

teenagers is drawn. Round your answers to at least four decimal places as needed.

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(a) Find the mean

p

.

The mean p is 0.75 .

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(b) Find the standard deviation

p

.

The standard deviation p is 0.0283 .

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(c) Find the probability that more than

78%

of the sampled teenagers own a smartphone.

The probability that more than

78%

of the sampled teenagers own a smartphone is

0.1446

.

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(d) Find the probability that the proportion of the sampled teenagers who own a smartphone is between

0.72

and

0.80

.

The probability that the proportion of the sampled teenagers who own a smartphone is between

0.72

and

0.80

is

0.817

.

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(e) Find the probability that less than

80%

of sampled teenagers own smartphones.

The probability that less than

80%

of sampled teenagers own smartphones is

0.222

.

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(f) Would it be unusual if less than

65%

of the sampled teenagers owned smartphones?

It (Choose one) be unusual if less than

65%

of the sampled teenagers owned smartphones, since the probability is

.