The Greenland ice sheet covers roughly 80% of the surface of Greenland, being the second largest body of ice in the world, after the Antarctic ice sheet. As the arctic climate is rapidly warming, the Greenland ice sheet has experienced record melting in the recent years. The following data gives the depth of the ice sheet (in m) measured at various locations during the summer months in the Northeast greenland National Park:
3115, 3133, 3123, 3145, 3125, 3131, 3127, 3120, 3118, 3124
Using this data, is there enough evidence that the average depth of the ice sheet is below 3140 m? Assume that the depth of the ice sheet is normally dstributed. Use a test of hypotheses of level alpha = 0.05.