Listed below are time intervals(min) between eruptions of a geyser. Assume that the"recent" times are within the past fewyears, the"past" times are from around 20 yearsago, and that the two samples are independent simple random samples selected from normally distributed populations. Do not assume that the population standard deviations are equal. Does it appear that the mean time interval haschanged? Is the conclusion affected by whether the significance level is 0.10 or 0.01?

Recent

78

91

90

78

56

101

62

87

69

89

83

84

56

82

74

101

61

Past

88

87

93

94

63

84

85

92

88

91

89

91

Let 1 be the recent times and let 2 be the past times. What are the null and alternativehypotheses?

A.

H0: 12

H1: 1=2

B.

H0: 1=2

H1: 12

C.

H0: 1=2

H1: 1>2

D.

H0: 1<2

H1: 1=2

Calculate the test statistic.

t=

nothing

(Round to two decimal places asneeded.)

Find theP-value.

P-value=

nothing

(Round to three decimal places asneeded.)

Make a conclusion about the null hypothesis and a final conclusion that addresses the original claim. Use a significance level of 0.10.

Fail to reject

Reject

H0 because theP-value is

greater than

less than or equal to

the significance level. There

is

is not

sufficient evidence that the mean time interval has changed.

Is the conclusion affected by whether the significance level is 0.10 or 0.01?

A.

No, the conclusion is not affected by the significance level because H0 is not rejected regardless of whether a significance level of 0.10 or 0.01 is used.

B.

Yes, the conclusion is affected by the significance level because H0 is rejected when the significance level is 0.01 but is not rejected when the significance level is 0.10.

C.

No, the conclusion is not affected by the significance level because H0 is rejected regardless of whether a significance level of 0.10 or 0.01 is used.

D.

Yes, the conclusion is affected by the significance level because H0 is rejected when the significance level is 0.10 but is not rejected when the significance level is 0.01.