An investigator wants to show that first-born children

Reference no: EM13634422

An investigator wants to show that first-born children score higher on IQ tests than second-borns. He takes a simple random sample of 400 two-child families in a school district, both children being enrolled in elementary school. He gives these children the WISC vocabulary test, with the following results:

-The 400 first-borns average 29 and their SD is 10.

-The 400 second-borns average 28 and their SD is 10.

(Scores are corrected for age differences.) He makes a two-sample z-test:

SE for first-born average: 0.5

SE for second-born average: 0.5

SE for difference= square root of (0.5^2 + 0.5^2)= 0.7

z=1/0.7=1.4, P=8%

Comment briefly on the use of statistical tests.

Reference no: EM13634422

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