5. There have been several reports that house plants grow at different rates if

Question

5. There have been several reports that house plants grow at different rates if they are exposed to music. To test this idea, you obtained 20 plants and randomly chose 10 for exposure to music while the remaining 10 were not exposed to any sounds. Unfortunately, two of the plants exposed to music died, leaving only 8 in that treatment group. Below are the results of the experiment. The data are plant growth in mm/wk. (2 points) Control 6.9 8.5 10.2 14.9 Music 10.3 5.4 13 6.9 2.4 9.5 7.2 15.1 18.2 14.8 16.4 11.2 a. Calculate the variance for each treatment. What is the F-calc for these data? b. Using the table on p. 270, what is the F-critical for these data? Of the three types of t-tests covered in chapter 12, which two could be used to compare the treatment means? c.

Explanation / Answer

H0 : 2 (control) = 2 (music)

Ha : 2 (control) 2 (music)

a. Variance for Control treatment s2c = 22.756

Variance of Music Treamtnet s2m = 11.645

F- calc = s2c  / s2m = 22.756/ 11.645 = 1.954

b. F- critical for dF1 = 9 and dF2 = 7

for alpha = 0.05 , F0.025,9,7 = 4.823

F0.975,9,7 = 0.238

so F - value is under the values of F- critical so we cannot reject the null hypothesis .

Variances are equal.

c. We have to use 2- sample t- test with equal variances.

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