Seasonal affective disorder (SAD) is a type of depression during seasons with le

Question

Seasonal affective disorder (SAD) is a type of depression during seasons with less daylight (e.g., winter months). One therapy for SAD is phototherapy, which is increased exposure to light used to improve mood. A researcher tests this therapy by exposing a sample of SAD patients to different intensities of light (low, medium, high) in a light box, either in the morning or at night (these are the times thought to be most effective for light therapy). All participants rated their mood following this therapy on a scale from 1 (poor mood) to 9 (improved mood). The hypothetical results are given in the following table.

Light Intensity Low Medium High Morning 5 Time of Day Night (a) Complete the F-table and make a decision to retain or reject the null hypothesis for each hypothesis test. (Round your answers to two decimal places. Assume experimentwise alpha equal to 0.05.) Time of day Intensity Time of day x Intensity Error

Explanation / Answer

Using Data Analysis tool pack in excel

Data ->Data Analysis ->Two way ANOVA with replication,the output is shown below

a)The table to be filled are boldly shown above.

b)Main effect of day=>Retain the null hypothesis as the p-value is 0.60 which is greater than 0.05.

c)Intensity main effect =>Reject the null hypothesis(p-value is 0.03<0.05).

d)Interaction effect=>Retain the null hypothesis(P-value = 0.72>0.05)

e)From the above the significant main effect is the intensity as it is significant at the 0.05 level of significance.

Critical value k=3 df =33

Q =3.47

APA

A post hoc test was conducted to measure the difference between the intensity effect.The results of the analysis showed that the difference is significant between low and high intensity.

Anova: Two-Factor With Replication SUMMARY Low Medium High Total Morning Count 6 6 6 18 Sum 33 38 42 113 Average 5.5 6.3333 7 6.277778 Variance 1.1 4.6667 2 2.683007 Night Count 6 6 6 18 Sum 32 43 43 118 Average 5.333 7.167 7.167 6.556 Variance 3.467 2.167 1.367 2.850 Total Count 12 12 12 Sum 65 81 85 Average 5.416667 6.75 7.083333 Variance 2.083333 3.295455 1.537879 ANOVA Source of Variation SS df MS F Time of Day 0.69 1 0.69 0.28 Intensity 18.67 2 9.33 3.79 Time of Day*Intensity 1.56 2 0.78 0.32 Error 73.83 30 2.46 Total 94.75 35

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