Final answer:
The values of t that will cause the researcher to not reject the null hypothesis are between -2.861 and 2.861.
Step-by-step explanation:
In this case, the researcher is conducting a two-tailed test with a 0.01 significance level (alpha = 0.01). The critical values for a two-tailed test with 20 degrees of freedom can be found using the t-distribution table. These critical values correspond to the values of t that will cause the researcher to not reject the null hypothesis.
The critical t-values for a two-tailed test with alpha = 0.01 and 20 degrees of freedom are -2.861 and 2.861. Therefore, if the calculated t-value falls within this range, the researcher will not reject the null hypothesis.
Therefore, the correct answer is: C. Between -2.861 and 2.861.