Warm Up Find the following: Mean ± 1 Std Deviation = N = 22 Mean = 23.27 Std Dev. = 2.78 Find the following: Mean ± 1 Std Deviation = Percentage of Data in this interval Mean ± 2 Std Deviation = Mean ± 3 Std Deviation = 14.93 17.71 20.49 26.05 28.83 31.61 26.05 and 20.49 16/22 = 72.72% 28.83 and 17.71 22/22 = 100% 31.61 and 14.93 22/22 = 100%

Test and Homework Review

Math II B Day 2 (1-5-11) Standard MM2D1A Today’s Question: Pose a question and collect sample data from at least 2 populations. Today’s Question: What is margin of error?

Warm Up

The mean of 45 numbers is 12. What would be the new mean if 5 additional numbers were added to the sample? 5, 14, 9, 25, 21

Vocab Population – the group of people or objects you are getting information about or sampling. Sample – a subset of the population supposedly representing the whole population

Sample Types Self Selected – people volunteer for the survey Systematic – a rule or formula is used to select those to be sampled. Convenience – easy to reach people are selected Random – each person has an equal chance to be selected

Identify the following Email Survey Every 15th person in the phone book 30 people standing in line at the bank Randomly selected people

Biased/Unbiased Unbiased – the sample is representative of the whole population Biased – the sample is not representative of the whole population.

Identify the following Asking people if they are religious At a church At the mall on a weekday At the mall on Sunday at 9:00 AM Asking people if they like baseball At a church At the mall on a weekday At the mall on Sunday at 9:00 AM

Pass out the survey… look at it but don’t go over it yet.

Margin of Error

Margin of Error Its basically saying we are off by this much. Because we did not sample the entire population Because each sample of people is not completely representative of the population.

Margin of Error The margin of error gives a limit on how much the responses of a sample would differ from the responses of the population.

Margin of Error Example In a survey of 990 workers, 30% said they eat at home during a typical work week. What is the margin of error? Give an interval that is likely to contain the exact percent of all workers who eat at home? ±0.032 or ± 3.2% 26.8% to 33.2%

Give an interval that is likely to contain the exact percent of all workers who eat at home? Responders who said Yes 30% MOE + 3.2% MOE – 3.2% 33.2 % 26.8 % So the actual number of people who eat lunch at home at least once in the week is somewhere between 26.8% and 33.2%. We do not know the actual number because we have not asked everyone.

If….. You polled people in the lunch room on whether they like school lunch or not. 45% of people said yes. The margin of error is 19.24%. How many people did you ask? X =

Recap The more people you ask the smaller the margin of error, the more sure your are, the more reliable your statistic. ±40% ±17% ±15%

Math 2 Election Coverage

True interval is between 58.85% to 59.15% Saxby has 59% Only 20% of the Georgia Polls have reported. 2,132,458 total people voted 20% x 2,132,458 votes have been counted 426,491 votes have been counted Margin of Error ± √(1/426,491) = 0.15% Since the interval is still over 50% we are confident that he is the winner. True interval is between 58.85% to 59.15%

Classwork Page 270 #4-7, #12-15 Page 275 #5-8

Homework Page 271 #1-3, #10-13, #20-23