Agenda

-Warm-up

- 2.3 Quiz

-2.4 Lesson

- Homework.

- –2.4 8-24 even

DESK

Notes/warm up

- Need a calculator today

LT K: I can use a confidence interval to make inferences about a population.

Discrete or continuous

1. A survey of 200 adults reports that 78% believe in extraterrestrial life. 2. A sample of 350 adults responded to a survey about the amount of time spent commuting to work. The sample mean was 34.5 min and the sample standard deviation was 1.7 min. 3. A survey of 500 schools reports that 87% lock all their doors after the first bell. 4. A random sample of 1500 calculators shipped is checked and 4% are defective. 5. A sample of 300 sockeyes salmon was taken and each fish was weighed. The sample mean was 6.10 lbs and the sample standard deviation was 0.15 lbs.

Warm-up 9/6

Discrete

Continuous

Discrete

Discrete

Continuous

Warm-up 9/6

Identify whether the questions is about discrete or continuous data, then find the 95% confidence interval.

1. A sample of 630 grocery store shoppers responded to a survey about the average cost of their groceries each week. The sample mean was $125 and the sample standard deviation was $20.

2. A satisfaction survey was given to 220 gym members. Ninety-one percent of the respondents in the sample reported that they work out regularly and intend to renew their contract with the gym for an additional year.

2.4 Statistically Significant

LTK : I can use a confidence interval to make inferences about a population.

95% confidence interval Conclusion/ is there a link between the two?

1) Identify the characteristic of interest/ results .

2) Find the 95% confidence intervals ( two or more)

3) Compared the confidence intervals If the confidence interval do not overlapped – it is statistically Significant If the confidence interval overlapped – Not Statistically Significant 4) Accept or reject your results Accept – Statically Significant Reject – Not Statistically Significant

Skills Practice pg. 289 # 21

1) Does attending the earlier class cause lower test scores than attending the later class? Is there a link between time of class and test scores 2) Done Earlier Class: 70.8 to 77.5 late: 78.1 to 83.9

no overlapped – it is statistically Significant 3)

4) Yes there is a link in time of class and test score.

It cannot be stated that having to get up earlier will cause lower test scores but base on my data there is evidence of a link between the test score and time of the class.

22. An amusement park wants to test a different method of loading riders on a popular ride to see whether average wait time decreases. The interval from 45.7 to 51.8 represents a 95% confidence interval for the population mean wait time using the original method. The interval from 44.4 to 46.0 represents a 95% confidence interval for the population mean wait time using the new method. Does the new method seem to decrease the wait time for the riders?

1) Does the new method decrease the wait time for the riders. or Is there a link between the new method and decreasing wait time?

2) Done New method: 44.4 to 46 mean wait time

Old Method: 45.7 to 51.8 mean wait time

3) 3) overlapped – Not Statistically Significant

4) No we can’t tell if the new method actually decrease wait time because the two 95% confidence interval over overlapped. - No link between new method and decreasing wait time.

Now we need to find the confidence intervals

1) Is there a link between running commercial and getting more votes?

2) Find confidence intervals Discrete Data (1 )P P

n

0.36(1 0.36)

1500

0.012

36 2 1.2 33.6

36 2 1.2 38.4

0.38(1 0.38)

1400

0.013

38 2 1.3 35.4

38 2 1.3 40.6

w/o Commercial w/commercial

overlapped – Not Statistically Significant

No we can’t tell if running commercial will get more votes because the 95% confidence interval overlapped.

10. In a poll of 330 girls at a school, 225 watch more than 2 hours of TV a day. In a poll of 314 boys at the same school, 235 of them watch more than 2 hours of TV a day.

Discrete

(1 )P P

n

0.68(1 0.68)

330

0.026

68 2 2.6 62.8

68 2 2.6 73.2

Is there a link to gender and the amount of time spent watching tv in a day .

0.75(1 0.75)

314

0.024

75 2 2.4 70.8

75 2 2.4 79.8

girls boys

overlapped – Not Statistically Significant

No link in gender and amount of time spent watching tv.