Statistics and Probability Answers

The average zone of inhibition (in mm) for mouthwash H as tested by medical technology

students have been known to be 9mm. A random sample of 10 mouthwash H was tested

and the test yielded an average zone of inhibition of 7.5 mm with a variance of 25mm. Is

there enough reason to believe that the antibacterial property of the mouthwash has

decreased? Test the hypothesis that the average zone of inhibition of the mouthwash is

no less than 9mm using 0.05 level of significance.

A family has four children find the probability that the family has equal number of sons and daughter.

It is claimed that last year, 65% of the people believed that there was an improvement in the country’s economy.

Suppose this year, only 270 out of the 450 people randomly selected believe that there is an improvement in the country’s

economy. Does this indicate that there is a decrease in the number of people who believes that there is an improvement in

the country’s economy? Use 0.05 significance level.

(Use critical value method)

A History teacher claims that the average height of Filipino males is 163 centimeters. A student taking up Statistics

randomly selects 20 Filipino males and measures their heights. Their heights in cm are shown below.

163 164 165 177

167 163 159 169

159 160 163 163

165 169 163 165

162 174 163 167

Do the collected data present sufficient evidence to indicate that the average heights of Filipino male is different

from 163 cm? Use 0.05 level of significance and assume that the population follows a normal distribution.

(Use critical value method)

The cashier of a fastfood restaurant claims that the average amount spent by customers for dinner is P 120. 00. A sample

of 50 customers over a month period was randomly selected and it was found out that the average amount spent for dinner

was P 112. 50. Using a 0.05 level of significance, can it be concluded that the average amount spent by customers is more

than P 120. 00? Assume that the population standard deviation is P 6.50.

(Use the critical value method)

80% area below it

Length (meter): 5 6 7 9 12 Weight (KG): 13 15 18 19 20 State which of the two characteristics of two items is more variable?

Five items was taken from the output of factory. The length and weight of 5 items are given below. Length (meter): 5 6 7 9 12 Weight (KG): 13 15 18 19 20

what is probability

 Suppose a random sample of 38 sports cars has an average annual fuel cost of K2218 and the standard deviation was K523. Construct a 90% confidence interval for μ. Assume the annual fuel costs are normally distributed.