An eyeglasses manufacturer is interested in finding out whether people can read a computer screen faster using glasses with specially coated lenses as opposed to glasses with regular uncoated lenses. Sixteen people are asked to read a computer screen for 20 minutes with the coated lenses; on a separate day, the same 16 people are asked to read a computer screen for 20 minutes using lenses without the coating. The number of pages read by each participant for each condition was collected, and the results are summarized here.

Lesson Fourteen An eyeglasses manufacturer is interested in finding out whether people can read a computer screen faster using glasses with specially coated lenses as opposed to glasses with regular uncoated lenses. Sixteen people are asked to read a computer screen for 20 minutes with the coated lenses; on a separate day, the same 16 people are asked to read a computer screen for 20 minutes using lenses without the coating. The number of pages read by each participant for each condition was collected, and the results are summarized here. Number of Pages Read With Coating X1 Without Coating X2 Mean X1 = 13.4 msec Mean X2 = 12.7 msec S X1 = 2.6 msec S X2 = 2.1 msec r = 0.64 1. For the experiment above, what type of statistic should you use to analyze your data? a. z -test for single samples b. t-test for single samples. c. t-test for independent samples. d. t-test for correlated samples. e. z-test for correlated samples. Is computer-synthesized speech as easy to understand as speech that is spoken by a human? To find an answer to that question, a researcher randomly assigned 20 people to one of two different groups. One group was asked to transcribe a 100 word statement "spoken" by a computer, and the other group was asked to transcribe the same 100 word statement spoken by a human. The results are summarized in the table below. Number of Errors Made Computer Read X1 Human Read X2 Mean X1 = 10 Mean X2 = 8 S X1 =4 SX2=3 2. For the experiment above, what type of statistic should you use to analyze your data? a. z -test for single samples b. t-test for single samples. c. t-test for independent samples. d. t-test for correlated samples. e. z-test for correlated samples.Ms. Yonrev thinks that the 25 students in her fourth-grade class are exceptionally bright. To test this hypothesis, she decides to compare her students' IQ scores to the entire U. S. population of fourth grade students. The results are summarized in the table below. IQ Scores Ms. Yonrev's Fourth Graders X1 U.S. Population of Fourth Graders X2 Mean X1 = 110 Mean X2 = 100 S X1 = 11 S X2 = 16 3. For the experiment above, what type of statistic should you use to analyze your data? a. z -test for single samples b. t-test for single samples. c. t-test for independent samples. d. t-test for correlated samples. e. z-test for correlated samples 4. What are the results of the appropriate statistical test on the data from Problem #2? a. t = 1.265 b. t = 2.995 C. z = 1.041 d. t = 1.745 e. z = 1.745 5. What is the critical value at p = .05 for the data in #2 and what is the conclusion of the analysis? a. z = 2.101, Reject the null hypothesis. b. t = 1.734, Fail to reject the null hypothesis. c. t= 1.734, Reject the null hypothesis. d. t= 2.101, Fail to reject the null hypothesis. e. z = 1.745, Fail to reject the null hypothesis.For this Lesson you will be given these formulas for the examination: X - HX estimated ox S Vn X - MX S est. Ox estimated o= Vn df = n - 1 X1 - X2 t = est. diff estimated diff = V (estimated ox, )2 + (estimated ox,)? estimated O diff = Si S Vm n2 dfindependent samples = (1 - 1) + (n2 - 1) D X1 - X2 t= t= est. diff est. diff est. Odiff = V(est. ox )2 + (est. ox,)2 - (2 . r . est. ox, . est. ox2) ED2 D2 n est. diff = n - 1 df correlated samples = number of pairs - 1