Eg Start This 1 pt Suppose a geyser has a mean The peubabalty that a randomly se

Question

Eg Start This 1 pt Suppose a geyser has a mean The peubabalty that a randomly selected time interval is longer than 66minutes i Round to four decimal places as needed) minutes is approximae The probability that the mean of a random sample of 9 time intervalts is more than 66 minutes is approximaely Round to four decimal places as needed ) Round to four decimal places as needed) vaniability in the he sample s t the popuiation mean is less than 66 minutes, then the probability that the sample mean of the time behoeen eruptons is greater than 66 minutes B The population mean is 60, and this is just a rare samping D. The F. The population mean must be more than 60 since the probability is so low mean may be less than 60 mean cannot be 60 since the probability is so low G. The popuiation mean is 60, and ths is an esample of a typical sampling res 0 here to

Explanation / Answer

a) mean = 60 , sd = 12

Z = (X - 60)/12

P(X > 66)

= P (Z>0.5)=0.3085

b)

when n = 9 , sd(Xbar) = 12/sqrt(9) = 4

P(Xbar > 66)

= P (Z>1.5)=0.0668

c)

when n = 21

sd(Xbar) = 12/sqrt(21)

= 2.618614

P(Xbar >66)

= P (Z>2.29)=0.011

d) decreases, variability decreases , increases

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