30 Discussion One Math 2 Discussion One: ions Suppose you are designing and cond

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30 Discussion One Math 2 Discussion One: ions Suppose you are designing and conducting a poll to see which of the Congressional candidates are popular in your area. ments 1. Discuss the following (17 points): the population that you are trying to predict, where and how are you selecting your sample, what sampling method would you use, how would you assure that you are selecting a representative sample, and show an example of how you would present your data. utor ? 365 (Note: You must post before seeingthe

Explanation / Answer

(a) The population consists of all the people of your area.?

(b) Sample is taken from the population of the area in order to decrease overall time and cost.

Sample is selected such that:-

1. Sample group accurately represents the larger population. If 50 percent of voters are female, then 50 percent of the sample group needs to be female. The same applies to characteristics like age, race and geographic location.

2. start with a perfectly random sample and then adjust the sample so that it closely matches the characteristics of the entire population.

3.  Create a mathematical model for the data, researchers can accurately predict the probability of future outcomes.

(c) 1. Earlier probability sampling was the standard method for polls. But in recent years, as fewer people respond to polls and the costs of polls have gone up, researchers have turned to non-probability based sampling methods. For example, they may collect data on-line from volunteers.

2. The most popular method for achieving a random sample is through random digit dialing (RDD). Start with a continually updated database of all listed telephone numbers in your area -- both landline and cell phones. If they only called the numbers in the database, then they'd exclude all unlisted numbers, which wouldn't be a truly random sample.Then analyze the database of listed numbers to identify all active blocks of numbers, which are area codes and exchanges (the second three digits) actively in use. The computers are then programmed to randomly dial every possible number combination in each active block.

(d) Representative samples are important as they ensure that all relevant types of people are included in your sample and that the right mix of people are interviewed. If your sample isn’t representative it will be subject to bias.

Since we  started with a perfectly random sample and then adjust the sample so that it closely matches the characteristics of the entire population and also our sample is accurately representing the larger population in terms of gender,age, race and geographic location.So we are selecting a representative sample.

(e) For example: Imagine a sample of 1,000 people . The researcher was interested in finding out the most popular candidate. The results show:

% Very satisfied/satisfied % Dissatisfied/very dissatisfied TOTAL

Females 50 50 100

Males 60 40 100

It could seem appropriate to state that females are less likely to be satisfied with the candidate than males. However, this does not take into account the confidence interval around the estimate.

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