Probability and Statistics

L.V. Co. has an average sale of ₱37 million per week from their products in all their outlets. An area manager found out that the average gross sales from the 28 outlets under her jurisdiction is ₱32.5 million per week with standard deviation of ₱1.5 million. Does the mean sales of all outlets differ from the mean sales of the 28 outlets under her jurisdiction? In the given problem, what statistical tool is suitable to use?

• t-test

• z-test

• ANOVA

• Chi-Square

A cellular battery manufacturer claims that his battery when fully charged has mean life of 24 hours with standard deviation of 4 hours. A dealer randomly chose sample of 35 batteries to be tested and resulted to 22.5 hours mean life. In the given situation, 22.5 hours is __________.

• sample mean

• number of sample

• sample standard deviation

• population standard deviation

According to a study, there is an increase on average monthly expenses of ₱250.00 for cell phone loads of Senior High School students in the city. Is there a reason to believe that the amount increased if sample of 60 students has an average monthly expense of ₱280.00 and the population standard deviation is ₱77.00? What is the tool to be used in computing the test value?

• z-test

• t-test

• left-tailed test

• alternative test

Which of the following defines the area encompassed by the values not included in the non-rejection region or also the area of the tails of the distribution?

• critical value

• rejection region

• level of significance

• population variance

In a left-tailed test with 𝛼=0.01, the critical value of z is:

• -2.576

• -2.330

• -1.960

• -1.645

For a two-tailed test with variance unknown, n= 16, and 𝛼=0.05, what is the critical value?

• ±2.092

• ±2.134

• ±2.145

• ±2.125

What is the critical value if the population variance is known, 𝑎=0.025, and it is a two-tailed test?

• 𝑧=±1.28

• 𝑧=±1.645

• 𝑧=±1.96

• 𝑧=±2.33

What is the rejection region of the given normal curve at the right?

• 𝑧≥1.28

• 𝑧≥1.645

• 𝑧≥1.96

• 𝑧≤2.33

Based on the graph, which of the following is TRUE?

• This is a two-tailed test.

• This is a right-tailed test.

• Level of significance is 0.025.

• The rejection region is 𝑡≤ -1.725.

To determine the critical region if population variance is known, use table for _____________ distribution.

• z

• t

• chi

• table