A researcher examined the effect of background noise level on memory performance of college students. Students were randomly assignment to one of two groups. Students in the first group were given a memory test in a room with a How level of background noise and students in the second group were given the memory test in a room with a high level of background noise. The memory scores of the two groups are shown below. Set alpha at .05 and determine if background noise level had a significant effect on memory scores. Low noise level scores: 8, 10, 6, 8, 10,6 (SD = 1.788854) High noise level scores: 1, 3, 4,7,5,4 (SD = 2) What is/are the critical value(s) for this problem? Select one: O a. +1.645 O b. -2.228 OC.-2.201 O d. +2.228 Pool Air