A researcher tests a sample of first-grade children for a school district to help the district identify areas in which the curriculum should be changed. The measure is a valid and reliable measure of intelligence. The researcher estimates the population mean for the intelligence scores and observes a large value for the standard error of the mean. The best thing the researcher could do to improve the estimate is.

A. test children in a different, more heterogeneous school district.
B. compute a confidence interval.
C. change the testing procedures to increase the variability of the test scores.
D. increase the sample size of children tested.

D. increase the sample size of children tested.

Explanation: When it is impossible to pefrom research based on an entire population, a good representative sample should be chosen with a reasonable sample size, the sample size refers to the number of observations which the researcher aims to use in his statistical research. From studies, in other to improve the reliability of our research and ensure it conforms to the which will have been obtained from using the population, a large sample size is imperative, as it reduces the deviation of result obtained from that obtained using the population. Increasing the sampling size reduces the standard error between the sample mean and population mean.

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