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p-VALUES & ALPHA

P-values are at first difficult to understand. They are the answer to your research question and hypothesis. See attached slides 66-69 in the power point presentation in Instructor Announcements Yellow Brick Road.

EXCEL MEGASTAT P-VALUES RELATION TO ALPHA & THE REJECT/RETAIN DECISION

REJECT @ .01 (BRIGHT YELLOW) RETAIN @ .01 (BLACK & WHITE)

←-------------------------------------------------/----------------------------------------------------------------------------→

.01

REJECT@ .05 (BRIGHT YELLOW) RETAIN @ .05 (BLACK & WHITE)

←---------------------------------------------------------------------------------/-------------------------------------------→

.05

←-------------------------------------------/-----------------------------------/---------------------------------------------→ .01 .05

(DULL YELLOW)

IF BETWEEN .011 AND .049

RETAIN @ .01 & REJECT @ .05

CAUTION - THE ALPHA LEVEL COULD FLIP THE DECISION

If the p-value is greater than Alpha: Retain the null. If the p-value is less than Alpha: Reject the null.

We reject the null hypothesis at the .05 alpha level of significance (p=.002). There is a difference between ….

We retain the null hypothesis at the .05 alpha level of significance (p=.15). There is no difference between ….

If the p-value = 1.56 E-5 that is Megastat saying the p-value is .00000156. It is 1.56 with 5 zero’s. A very small number. It is also bright yellow. Reject. There is a significant difference.

ALPHA JUSTIFICATIONS

The nominal Alpha criterion level is set at .05 by this author as a reasonable probability for detecting a type I error.

The Alpha level of significance is set at .05 as directed by management.

The Alpha level of significance is set at .05 as indicated in previous research.

The Alpha level is set at .05 as this researcher’s conviction of the importance of this study.

The Alpha level of significance is set at .05 as used in prior research.

The Alpha level is resolved to be .01 as determined by the seriousness of this problem.

The Alpha level is .01 because injury and loss of human life is a possibility.

The Alpha level is resolved to be .01 because of the importance of this issue to the company.

The Alpha level is .01 because the loss may amount to 100 million dollars.

(The underlined words may be changed).