Question

35 people are randomly selected and the accuracy of their wristwatches is checked, with positive errors representing watches that are ahead of the correct time and negative errors representing watches that are behind the correct time. The 35 values have a mean of 115sec and a population standard deviation of 199sec. Use a 0.02 significance level to test the claim that the population of all watches has a mean of 0sec (use a two-sided alternative).

How to put into TI 84?

(1 point) A study is conducted to determine if a newly designed text book is more helpful to learning the material than the old edition. The mean score on the final exam for a course using the old edition is 75. Ten randomly selected people who used the new text take the final exam. Their scores are shown in the table below. Person ABCDEFGHIJ Test Score 92 82 95 84 78 73 87 69 97 72 Use a 0.01 significance level to test the claim that people do better with the new edition. Assume the standard deviation is 10.2. (Note: You may wish to use statistical software.) (a) What kind of test should be used? O A. One-Tailed OB. TWO-Tailed OC. It does not matter. (b) The test statistic is 2.53 (rounded to 2 decimals). (c) The P-value is 0.016 (d) Is there sufficient evidence to support the claim that people do better than 75 on this exam? OA. Yes OB. No (e) Construct a 99% confidence interval for the mean score for students using the new text. 72.733 << 93.067

Answer 1

In this example, we are told that the population

standard deviation is thought to be 199 sec and

we have a large enough sample size. Therefore, a

z-interval can be used to calculate the

confidence interval.

Step 1: Go to the z-interval on the calculator.

Press [STAT]->Calc->7. Z-interval [ENTER]

Step 2: Highlight STATS

Since we have statistics for the sample already

calculated, we will highlight STATS at the top. If

you had a list of data instead, you could enter it

into L1 and then use DATA. This is really only

useful for small data sets.

Step 3: Enter Data

Notice that the calculator asks for sigma (the

population standard deviation) – this should help

you remember that you shouldn’t be using this

unless you have sigma already.

i.e. put, $\sigma$ (sigma )= 199 i.e. population standard deviation

Xbar (mean) = 155 i.e. sample mean

n = 35 i.e. sample size

C - Level : .99 i.e. confidence level

Step 4: Calculate and interpret

Please make sure to read the explanation of how

to interpret intervals in general. It is very easy to

misunderstand what they truly mean! Highlight

CALCULATE and then press ENTER to get your

interval.