Question: A health psychologist was interested to see if self-reported stress scores resulted in significantly different Cortisol measures. She asked a sample of patients to complete a stress questionnaire and categorised them as either being "High Stress", "Medium Stress", or "Low Stress", depending upon their responses on the questionnaire. She then measured their salivary Cortisol levels, which could range from 0 to 6 (the higher the number, the higher the Cortisol level - the measure can be assumed to be at least interval in nature).
The following data were obtained from the patients:
|
High Stress
|
Medium Stress
|
Low Stress
|
|
3.816622
|
1.047012
|
1.792735
|
|
3.791716
|
2.146911
|
1.422288
|
|
4.112685
|
2.014023
|
1.675610
|
|
3.877990
|
1.799969
|
1.297839
|
|
4.148395
|
2.402153
|
1.745501
|
|
4.094494
|
2.232413
|
1.461551
|
|
4.203315
|
1.934752
|
1.348446
|
|
3.969050
|
2.298638
|
1.839337
|
|
3.682800
|
1.416870
|
1.338415
|
|
3.922470
|
2.188166
|
2.003368
|
|
3.943557
|
2.010698
|
1.146607
|
|
4.095992
|
0.758262
|
1.297852
|
|
4.228955
|
1.704794
|
2.570737
|
|
3.594576
|
1.611385
|
1.226470
|
|
4.205555
|
1.758421
|
1.813969
|
|
3.720655
|
2.038071
|
1.903663
|
|
3.612999
|
2.219717
|
1.234318
|
|
4.018633
|
2.582688
|
1.402865
|
|
4.141084
|
3.044053
|
0.577023
|
|
3.816622
|
2.427801
|
1.250202
|
Are there significant differences in the Cortisol levels of these three groups?