What is the consequence of a Type II error?

a. concluding that a treatment has an effect when it really does
b. concluding that a treatment has no effect when it really has no effect
c. concluding that a treatment has no effect when it really does
d. concluding that a treatment has an effect when it really has no effect

http://www.investopedia.com/terms/t/type-ii-error.asp

The consequence of a Type II error is:

c. concluding that a treatment has no effect when it really does.

To understand how to identify the consequence of a Type II error, it is important to understand the concept of hypothesis testing and its components:

1. Null hypothesis (H0): The assumption that there is no real effect or difference between groups or treatments.
2. Alternative hypothesis (Ha): The belief that there is a real effect or difference between groups or treatments.

In hypothesis testing, we try to gather evidence to either support or reject the null hypothesis. However, there is always a possibility of making errors in our conclusions. In the case of a Type II error, we fail to reject the null hypothesis (conclude that there is no effect), when in fact, the alternative hypothesis is true (there is a real effect).

So, in the context of the question, a Type II error occurs when we incorrectly conclude that a treatment has no effect (null hypothesis), when in reality, it does have an effect (alternative hypothesis).

The consequence of a Type II error is option c. concluding that a treatment has no effect when it really does.