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A scrap metal dealer claims that the mean of his cash scales is "no more than $80," but an Internal Revenue Service agent believes the dealer is truthful. Observing a sample of 20 cash customers, the agent finds the mean purchases to be $91, with a standard deviation of $21. Assuming the population is approximately normally distributed, and using the 0.05 level of significance, what is the calculated value of test statistic

Answer :

JeanaShupp

Answer: 2.3425

Step-by-step explanation:

As per given , we have

[tex]\mu=80[/tex]

n = 20

[tex]\overline{x}=91\\\\ s=21[/tex]

We assume that the population is approximately normally distributed.

Since population standard deviation is unknown , so we use t-test.

Test statistic : [tex]t=\dfrac{\overline{x}-\mu}{\dfrac{\sigma}{\sqrt{n}}}[/tex]

[tex]\\\\ t=\dfrac{91-80}{\dfrac{21}{\sqrt{20}}}=2.342547405\approx2.3425[/tex]

Hence, the calculated value of test statistic = 2.3425

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