In a test, the 10 students in group 1 get a mean score of 43%. The 15 students in group 2 get a mean score of 57%. Hank says, " The mean score for all 25 students is 50%.&q…

Question

In a test, the 10 students in group 1 get a mean score of 43%.

The 15 students in group 2 get a mean score of 57%.

Hank says, " The mean score for all 25 students is 50%."
What mistake has Hank made?

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What is the correct mean score for all 25 students?

Answer 1

The mistake is that he forgot that the groups were not equal! one group was bigger than another, but he treated them as if they were equal

the real mean is calculated like this:

(43*10+15*57)/25=

(1285)/25=51.4


the real mean was 51.4