Experiment 2:

Texas Instruments has programmed their calculators with an Automatic Power Down (APD) to turn the calculator off to prolong the life of the batteries if it has not been used for five minutes (300 seconds).The population is normally distributed.Turn your calculator on and leave it alone. Record the time (in seconds) that it takes your calculator to automatically turn off and enter it in the last slot (so that n=7).

298

295

303

292

297

301

Conduct a hypothesis test at the .10 level of significance to test the claim that TI calculators turn off in under300 seconds of non-use.

1. Let =

H_O:

H_a:

1. Why is it appropriate to use t to determine the critical value(s) for this hypothesis test?

,

• Draw a bell curve and shade (or describe) the rejection region. See excel directions on the next page to calculate critical value.

• Click on the cell H6. Then click Formulas More Functions Statistical T.Inv. A menu called Function Argumentsshould appear.
  • Probability is the area to the leftof the critical value in the t-distribution with n-1 degrees of freedom.
  • Deg_freedomis the degrees of freedom. Recall df = n-1.

Record the Critical Value from cell H6. t* = ___________ Round to the thousandths place and label the CV on the bell curve above.

1. Calculate the test statistic for the second experiment:

• Click on cell H2. Type =average(B2:B8). This calculates the sample mean of the second experiment.

Record this value rounded to the three places x-bar = __________.

• Click on cell H3. Type=stdev(B2:B8). This calculates the sample standard deviation of the second experiment.

Record this value rounded to three places s = ________.

• Next, click on cell H4 and enter the formula =H3/SQRT(COUNT(B2:B8)). This value is the standard deviation of the sample means (this is called the standard error of the mean), and can be calculated by hand using formula .

Record this value rounded to three places SE = _________.

• Click on the cell H5. Then click Formulas More Functions Statistical Standardize. A menu called Function Argumentsshould appear.
  • X is the value you want to standardize. This is the sample mean. Enter H2.
  • Mean is the mean of the sampling distribution. This is the hypothesized mean from your hypotheses in part a.
  • Standard deviation is the standard deviation of the sample means (standard error). Enter H4.
• Record the Test Statistic from cell H5. t_stat = ___________.

1. Use the test statistic to make the conclusion (explain why and interpret in context).

Use the p-value method to make all of your conclusions on Experiment #3 and #4.

call time	calculator	method 1	method 2			Experiment 1	Experiment 2	Experiment 3	Experiment 4
24	298	85	84		Mean	17.33333333		81.375	90.625
18	295	83	90		Standard Deviation	4		6.759913355	5.0691645
16	303	92	98		Standard Error	0.730296743		2.389990287	-0.3487295
28	292	68	96		Test Statistics	-3.651483717		-4.95535714	1.7702074
10	292	82	91		Critical value	-1.174986792			0.7375461
12	301	81	93		p-value
20		82	89
18		78	84
24
17
6
14
18
26
14
20
8
6
10
10
24
25
14
24
22
16
18
16
20
22