The next 10 questions (11 to 20) concern the following data. A psychologist administered a new dementia ratingscale on 344 participants, and allocated them into three groups: normal, mild cognitive impairment (MCT), anddementia based on their clinical notes. The mean M) total and subtest scores and standard deviations SD) for thenew scale are sum mmarized in the table below.

【題組】11. If he wants to compare the testing scores between all groups, the null hypothesis will be
(A). the performance of the normal and MCI groups will be better than that of the dementia group
(B). true with 95% probability
(C). the performance of all groups is not significantly different
(D). true with 5% probability