Amanufacturer of new light bulbs claims the average lifetime of its long-life bulb is more than 4000 hours. to test this claim, a reputable testing firm took a random sample of 100 bulbs and life tested them. the testing firm found the average life of the sample to be 4500 hours with a sample standard deviation, s = 400 hours. the value of the test statistic for this problem isa 1.25b -1.25c 12.5d -12.5e none of the values listed

C. 12.5

Step-by-step explanation:

Given : A manufacturer of new light bulbs claims the average lifetime of its long-life bulb is more than 4000 hours.

Population mean :  

Sample size : n= 100

Sample mean :

Standard deviation:

The value of test-statistic is given by :-

Hence, the value of the test statistic for this problem is 12.5.

2.2°  

step-by-step explanation:

let θ = the angle of elevation.

tanθ =77/2020

tanθ = 0.038 12

      θ = tan⁻¹0.038 12

      θ = 2.2°

idk wbu

step-by-step explanation: