The earth's temperature (which affects seed germination, crop survival in bad weather, and many other aspects of agricultural production) can be measured using either ground-based sensors or infrared-sensing devices mounted in aircraft or space satellites. Ground-based sensoring is tedious, requiring many replications to obtain an accurate estimate of ground temperature. On the other hand, airplane or satellite sensoring of infrared waves appears to introduce a bias in the temperature readings. To determine the bias, readings were obtained at five different locations using both grouns- and air-based temperature sensors. The readings are listed below:

Location           Ground       Air

1               46.9           47.3

2               45.4           48.1

3               36.3           37.9

4               31.0           32.7

5               24.7           26.2

Do the data present sufficient evidence to indicate a bias in the air-based temperature readings? Explain.

Estimate the difference in mean temperatures between ground- and air-based sensors using a 95% confidence interval.

How many paired observations are required to estimate the difference between mean temperatures for ground- versus air-based sensors correct to within .2°C, with probability approximately equal to .95.