Listed below are time intervals (min) between eruptions of a geyser. Assume that the "recent" times are within the past few years, the "past" times are from around 20 years ago, 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 has changed? Is the conclusion affected by whether the significance level is 0.10 or 0.01?

recent 78 90 89 78 58 101 61 87 71 87 83 82 56 81 75 101 62

past 89 88 93 94 64 86 85 92 88 91 88 91

test statistic

p value