Exam 15: Statistical Evaluation of Data

A researcher records the average age for a group of 25 preschool children selected to participate in a research study.The average age is an example of a statistic.

Explain why a measure of effect size is recommended to accompany the result from a hypothesis test.

Explain the concept of statistical significance.Be sure that the concept of an alpha level in included in your explanation.

Values such as Cohen's d or r² (the percentage of variance accounted for)are used to measure

Describe what is measured by the mean and what is measured by the standard deviation for a set of scores.Describe the set of scores in a sample with a mean of M = 40 and a standard deviation of SD = 4.(Where are most of the scores located? Where are they centered? What range of values do they cover?)

A researcher interested in language development obtains a sample of 25 three-year-old girls and a sample of 25 three-year-old boys.Each child is given a vocabulary test and the researcher computes the mean score for each sample.The difference between the two sample means is an example of a

By convention,it has been determined that alpha levels should be set no larger than

A Type I error means that the hypothesis test has failed to detect a real treatment effect.

For a within-subjects study evaluating the mean difference between two treatment conditions,the appropriate hypothesis test is

What outcome is likely to occur for a hypothesis test evaluating a treatment that has a very small effect?

It is always possible that patterns observed in sample data do not accurately represent patterns in the population.

When a research report demonstrates a significant treatment effect at the .05 level,you can be more confident that the effect is real than if the researcher had reported a significant effect with an alpha level of only .01.

For scores measured on a nominal scale of measurement (for example,job classification),which measure of central tendency is appropriate?

A researcher is interested in the sleeping habits of students at the local state college.The entire set of students enrolled at the college is an example of a

Identify the two basic concerns with using a correlation to measure split-half reliability and explain how these concerns are addressed by Spearman-Brown,K-R 20,and Cronbach's alpha.

Cohen's kappa is used to correct for chance agreements when computing inter-rater reliability.

Statistical methods that use sample data to answer general questions about a population are called

A researcher who is interested in studying how humidity affects the eating behavior of rats obtains 25 rats to participate in a research study.The group of 25 rats is called a

If a sample is selected from a population,the sample mean is essentially guaranteed to be different from the population mean.In general,the naturally occurring difference between a sample statistic and the corresponding population parameter is called

For a study comparing the proportion of registered Democrats who approve of the president's economic policy with the corresponding proportion for registered Republicans,the appropriate hypothesis test is