"We are 95% confident that, in the population,people who only sleep for 8 hours will score -2.42 to -.38 points higher than people who sleep for only 4 hours."

This is the confidence interval that showed up my spss output but how is -2.42 the lower limit? i'll add some screenshots below

Question

"We are 95% confident that, in the population,people who only sleep for 8 hours will score -2.42 to -.38 points higher than people who sleep for only 4 hours."

This is the confidence interval that showed up my spss output but how is -2.42 the lower limit?  i'll add some screenshots below

rzlearner · Answer

Here is the description of the study I have to analyze as well

"Sam Sleep researcher hypothesizes that people who are allowed to sleep for only four hours will score significantly lower than people who are allowed to sleep for eight hours on a cognitive skills test. He brings 50 participants into his sleep lab and randomly assigns them to one of two groups. In one group he has participants sleep for eight hours and in the other group he has them sleep for four hours. The next morning he administers the SCAT (Sam's Cognitive Ability Test) to all participants. (Scores on the SCAT range from 1-9 with high scores representing better performance).Please analyze this data using a two-tailed test at the α = .05 level."