Researchers have a samSuppose that test scores are normally distributed with an unknown mean and standard deviation. The scores of 20 students are used to estimate the mean score. Use a calculator to find the t -score that should be used to find the 90 % confidence interval for the population mean score. Round your answer to three decimal places.ple size of 24 , and they are using the Student's t-distribution. What are the degrees of freedom and how would they notate this distribution