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In: Statistics and Probability

A cognitive psychologist believes that memory for pictures is superior to memory for words. To test...

  1. A cognitive psychologist believes that memory for pictures is superior to memory for words. To test this hypothesis, the psychologist performs an experiment in which students from an introductory psychology class are used as participants. Ten randomly selected students view 30 slides with nouns printed on them, and another group of eight randomly selected students views slides with pictures of the same nouns. Each slide is presented for 4 seconds. After viewing the slides, participants are given a recall test, and the number of correctly remembered items is measured. The summary data follow:

Nouns     Pictures

n1 = 10      n2 = 8

M1 = 20    M2 = 22

SS1 = 30   SS2 = 40

Is there a difference between nouns and pictures in the number of words recalled? Use a two-tailed test with α = 0.05.

(1) What type of statistical test is appropriate for this research question?

(2) State the null and alternative hypotheses using statistical notation OR using plain English (a sentence for each).

(3) What are the degrees of freedom and critical t-values for this test?

(4) Calculate the pooled variance.

(5) Compute the test statistic

(6) What is your decision? And what does that decision mean, or how would you interpret/explain your decision?

(7) Construct the 95% confidence interval for the mean difference between the two conditions, µ1-µ2.

(8) Would you reject or fail to reject H0 based on the 95% confidence interval? How do you know?

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