Final answer:
A 95% confidence interval would not include the value 34, as it would be narrower than the 98% confidence interval of 35 to 40 units, and 34 is already lower than the lower bound of the 98% interval.
Step-by-step explanation:
If your friend computes a 98% confidence interval for the population mean as 35 to 40 units, and you are wondering whether a 95% confidence interval would include the value 34, the answer is 'b. No.' When we construct a confidence interval for a population mean, the confidence level indicates the degree of certainty we have that our interval contains the true population mean. A higher confidence level produces a wider interval because we are more certain that the interval includes the true population mean. In contrast, a lower confidence level produces a narrower interval.
Given that your friend's 98% confidence interval is 35 to 40, reducing the confidence level to 95% would result in a narrower interval. Since 34 is less than the lower bound of the 98% confidence interval (35), it would not be included in the narrower 95% confidence interval. Therefore, the 95% confidence interval for the population mean would not include the value 34.