Ethics codes in companies


H0 :   π  =  0.72
HA :   π  ≠  0.72

Use this diagram to illustrate the doubling of the tail area to find the p-value for a 2-tailed test.

Drag the slider to x = 97, the observed number of companies with ethics codes. The bar chart highlights the smaller of the two tail areas and this tail probability is doubled to give the p-value (0.1436).

Since there is over 14% probability that the sample proportion is this far from the population proportion, there is no evidence that the propn of companies with ethics codes has changed.


In 1999, The Conference Board surveyed 124 companies and found that 97 had their own ethics codes ("Business Bulletin", Wall Street Journal, Aug 19, 1999). In 1997, it was believed that 72% of companies had ethics codes, so is there any evidence that the proportion has changed?