statistics/ Help!-thanks!

posted by .

The producers of a new toothpaste claim that it prevents more cavities than other brands of toothpaste. A random sample of 60 people use the new toothpaste for 6 months. The mean number of cavities at their next check up is 1.5. In the general population the mean # of cavities after a 6 month check up is 1.73 (@= 1.12).
a) is it 1 or 2 tailed test? (I think one- tailed)
b) What are the Ho and Ha for this study? I think:
Ho: µ = µ1 or µ cavities from new toothpaste= cavities any other brand toothpaste
Ho: µ0>µ1 or µ cavities from new toothpaste> µ cavities with any other brand toothpaste
Ha: µ0<µ1 or µ cavities from new toothpaste<µ cavities with any other brand toothpaste

c) Compute Zobt -I don't know how
d) What is Z cv?- Also don't know.
e) Should Ho be rejected (I think yes)
f) Determine the 95% confidence interval for the population mean, based on the sample mean.

• statistics/ Help!-thanks! -

I would phrase the hypotheses this way:

Ho: µ ≥ 1.73
Ha: µ < 1.73

This would be a one-tailed test since Ha is showing a specific direction (less than).

Use a z-test:
z = (sample mean - population mean)/(standard deviation divided by the square root of the sample size)

Once you have the z-test statistic, compare to a critical value from a z-table. If the test statistic exceeds the critical value from the table, reject the null. If the test statistic does not exceed the critical value from the table, you cannot reject the null. You can draw your conclusions from there.

From looking at the data, it does appear Ho will be rejected.

Confidence interval formula:
CI95 = mean ± 1.96(sd/√n)
...where sd = standard deviation and n = sample size.

I hope these few hints will help get you started.

Similar Questions

1. scientific method

http://classweb.gmu.edu/biologyresources/writingguide/ScientificPaper.htm What are the steps of the scientific method?
2. biology

What is the difference between a control group and an experimental group?
3. science

I have an experiment to do with active transport and osmosis with an egg?
4. Stats

5. The board of directors for Procter and Gamble is concerned that only 19.5% of the people who use toothpaste buy Crest toothpaste. A marketing director suggests that the company invest in a new marketing campaign which will include …
5. Economics

It is assumed that the toothpaste market is perfectly competitive and the current price of a case of toothpaste is \$42.00. CPI has estimated its marginal cost function to bas follows: MC=.006Q. The Board would like to know how many …
6. Calculus

it is assumed that the toothpaste market is perfectly competitive and the current price of a case of toothpaste is 42.00. CPI (the company) has estimated its marginal cost function to be as follows: MC (Marginal Costs) =.006Q (Quantity). …
7. marketing

Binomial probability distributions are used in business, science, engineering, and other fields. Suppose you work for a marketing agency and have to create a television ad for Brand A toothpaste. The toothpaste manufacturer claims …
8. Math

1.) Solve the system by graphing. You may use paper or a calculator. 2x - y = 8 x + 3y = 11 2.) The revenue for a certain brand of toothpaste is y = 2.5x where 'x' is the number of tubes of toothpaste sold and 'y' is the total income …
9. Math Help!

1.) Solve the system by graphing. You may use paper or a calculator. 2x - y = 8 x + 3y = 11 2.) The revenue for a certain brand of toothpaste is y = 2.5x where 'x' is the number of tubes of toothpaste sold and 'y' is the total income …
10. Chemistry

A toothpaste contains 0.220 % by mass sodium fluoride used to prevent dental caries and 0.32 % by mass triclosan C12H7Cl3O2, an antigingivitis agent. One tube contains 119 g of toothpaste. How many fluoride ions, F−, are in the …

More Similar Questions