Question

According to the manufacturer of a backup UPS device, the normal output voltage is 120 volts. The sample of 40 measured voltage amounts from a unit have a mean of 123.59 volts and a standard deviation of 0.31 volts. Use a 0.05 significance level to test the claim that the sample is from a population with a mean equal to 120 volts.

Answer 1

Answer:

z = 1.83<1.96

null hypothesis is accepted

The sample is came from a population mean

Step-by-step explanation:

Step :-1

The sample of 40 measured voltage amounts from a unit have a mean of 123.59 volts and a standard deviation of 0.31 volts

given sample size n =40

mean of the sample ×⁻ = 123.59 volts

standard deviation of sample σ = 0.31 volts

Step2:-

Null hypothesis :-

the sample is from a population with a mean equal to 120 volts.

H₀ : μ =120

Alternative hypothesis:-

H₁ : μ ≠120

level of significance:- α =0.05

Step 3:-

The test statistic

$z = \frac{x_{-}-mean }{\frac{S.D}{\sqrt{n} } }$

substitute values and simplification

$z = \frac{123.59-120}{\frac{0.31}{\sqrt{40} } }$

on simplification we get the calculated value

z = 1.83

The tabulated value z =1.96 at 0.05 % level of significance

Conclusion:-

Calculated Z < The tabulated value z =1.96 at 0.05 % level of significance

so the null hypothesis is accepted

The sample is came from a population mean