Question

A company has developed a new ink-jet cartridge for its printer that it believes has a longer life-time on average than the one currently being produced. To investigate its length of life, 40 of the new cartridges were tested by counting the number of high-quality printed pages each was able to produce. The sample mean and standard deviation were determined to be 1511.4 pages and 35.7 pages, respectively. The historical average lifetime for cartridges produced by the current process is 1502.5 pages. Calculate the appropriate test statistic to test the hypotheses.

Answer 1

Explanation:

Given that

mu = 1502.5 pages

Sample mean x bar = 1511.4 pages

Std deviation =s= 35.7 pages

Sample size n = 40

By assuming random samples since only sample std dev is know we can say that sample mean x bar follows a t distribution with

mean =1511.4 and std error =
`(35.7)/(√(40) ) \\=5.64`

Test statistic t = Mean diff/STd error = 1.613

df = 39