Consider a small scale example, comparing how temperatures have changed in the us from1968 to 2008. the daily high temperature reading on january 1 was collected in 1968 and 2008 for 51 randomly selected locations in the continental us. then the difference between the two readings (temperature in 2008 - temperature in 1968) was calculated for each of the 51 different locations. the average of these 51 values was 1.1 degrees with a standard deviation of 4.9 degrees. we are interested in determining whether these data provide strong evidence of temperature warming in the continental us. (does the data provide evidence that the true mean temperature is greater in 2008 than in 1968? ) justify fully at the 5% significance level.