Final answer:
The conventional level of significance adopted in psychology is p < 0.05, which means if the p-value is less than 0.05 the null hypothesis is rejected, otherwise it is not.
Therefore, the correct answer is: option a) p < 0.05
Step-by-step explanation:
The level of significance is defined as the fixed probability of wrong elimination of null hypothesis when in fact, it is true.
The conventional level of significance typically adopted in psychology is p < 0.05. This means that for a hypothesis test, if the calculated p-value is less than 0.05, the decision would be to reject the null hypothesis, indicating there is statistically significant evidence against it.
Conversely, if the p-value is not less than 0.05, the decision would be to not reject the null hypothesis, suggesting that the evidence is not strong enough to do so.
For instance, if the p-value is calculated to be 0.0187, it is considerably smaller than 0.05, which allows researchers to be confident in rejecting the null hypothesis.
However, if the p-value is 0.2150, and the level of significance is set at 5 percent, the right decision is not to reject the null hypothesis because the p-value is larger than the significance level.