Final answer:
To calculate a 95% confidence interval for the class average grade, we need the correct sample mean and standard deviation of the grades. Then we can determine the t-value for the given confidence level and degrees of freedom, and compute the margin of error. With these, the confidence interval's lower and upper limits can be found and rounded to one decimal place.
Step-by-step explanation:
To construct a 95% confidence interval for the average class grade, we first need to calculate the sample mean and standard deviation.
Unfortunately, the grades provided in the question appear to be incomplete or incorrectly formatted.
Assuming the grades are correctly listed elsewhere, the steps to find the confidence interval would be as follows.
Calculate the sample mean (μ) by adding all the grades and dividing by the number of students (in this case, 6).
Compute the sample standard deviation (s).
Use the t-distribution to find the t-value that corresponds to a 95% confidence level and the appropriate degrees of freedom (n-1).
Calculate the margin of error by multiplying the standard deviation by the t-value, and dividing by the square root of the sample size.
Add and subtract the margin of error from the sample mean to get the lower and upper limits of the confidence interval.
Without the correct data, the specific confidence interval cannot be calculated. If the correct data were available, the response would include the numerical confidence interval rounded to one decimal place.