CBSE Class 12 Applied Mathematics — Inferential Statistics

For the purpose of t-test of significance, if a random sample of size 34 is drawn from a normal population, then the degree of freedom $(\nu)$ is :

The range of variable t of the t-distribution is :

A soap manufacturing company was distributing a particular brand of a soap through a large number of retail shops. Before a heavy advertisement campaign, the mean sales per week per shop was 140 dozen. After the campaign, a sample of 26 shops was taken and mean sales was found to be 147 dozen with standard deviation 16. Can you consider the advertisement campaign effective ? [Given $t_{25}(0.05) = 2.06$]