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The following data a delayed discounting study. The participants are asked how m

ID: 3234103 • Letter: T

Question

The following data a delayed discounting study. The participants are asked how much they would take today instead of waiting for a specific delay period to receive $1000. Each participant responds to all 5 of the delay periods. Use a repeated-measures ANOVA with alpha = .01 to determine whether there are significant differences among the 5 delay periods for the following data: The endorphins released by the brain act as natural painkillers. For example. Gintzler (1980) monitored endorphin activity and pain thresholds in pregnant rats during the days before they gave birth. The data showed an increase in pain threshold as the pregnancy progressed. The change was gradual until 1 or 2 days before birth, at which point there was an abrupt increase in pain threshold. Apparently a natural painkilling mechanism was preparing the animals for the stress of giving birth. The following data represent pain-threshold scores similar to the results obtained by Gintzler. Do these data indicate a significant change in pain threshold? Use a repeated- measures ANOVA with alpha =.01.

Explanation / Answer

Result:

Ho: There is no change in pain threshold.

H1: There is a change in pain threshold

Repeated measure ANOVA F(3,12)=101.25, P=0.000 which is < 0.01 level of significance.

Ho is rejected.

We conclude that there is significant change in pain threshold.

Minitab OUTPUT:

General Linear Model: pain versus Subject, Days

Method

Factor coding (-1, 0, +1)

Factor Information

Factor   Type    Levels Values

Subject Random       5 A, B, C, D, E

Days     Fixed        4 1, 3, 5, 7

Analysis of Variance

Source     DF   Adj SS   Adj MS F-Value P-Value

Subject   4   208.00 52.000    19.50     0.000

Days     3   810.00 270.000   101.25    0.000

Error     12    32.00    2.667

Total      19 1050.00

Model Summary

      S    R-sq R-sq(adj) R-sq(pred)

1.63299 96.95%     95.17%      91.53%

Coefficients

Term        Coef SE Coef T-Value P-Value   VIF

Constant 45.000    0.365   123.24    0.000

Subject

A        0.000    0.730     0.00    1.000     *

B       -1.000    0.730    -1.37    0.196     *

C        5.000    0.730     6.85    0.000     *

D        1.000    0.730     1.37    0.196     *

Days

1       10.000    0.632    15.81    0.000 1.50

3        1.000    0.632     1.58    0.140 1.50

5       -5.000    0.632    -7.91    0.000 1.50

Regression Equation

pain = 45.000 + 0.0 Subject_A - 1.000 Subject_B + 5.000 Subject_C + 1.000 Subject_D

       - 5.000 Subject_E + 10.000 Days_1 + 1.000 Days_3 - 5.000 Days_5 - 6.000 Days_7

Equation treats random terms as though they are fixed.

Fits and Diagnostics for Unusual Observations

Obs   pain    Fit Resid Std Resid

3 49.00 46.00   3.00       2.37 R

4 52.00 55.00 -3.00      -2.37 R

R Large residual

Expected Mean Squares, using Adjusted SS

            Expected Mean Square

   Source   for Each Term

1 Subject (3) + 4.0000 (1)

2 Days     (3) + Q[2]

3 Error    (3)

Error Terms for Tests, using Adjusted SS

                                Synthesis

   Source   Error DF Error MS of Error MS

1 Subject     12.00    2.6667 (3)

2 Days        12.00    2.6667 (3)

Variance Components, using Adjusted SS

Source   Variance % of Total    StDev % of Total

Subject   12.3333      82.22% 3.51188      90.68%

Error     2.66667      17.78% 1.63299      42.16%

Total          15              3.87298

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