Statistically Figuring Sample Size When designing a study, the sample size is an important consideration because the larger the sample size, the more data you have, and the more precise your results will be (assuming high-quality data). If you know the level of precision you want (that is, your desired margin of error), you can calculate the sample size needed to achieve it. To find the sample size needed to estimate a population mean ( µ), use the following formula: In this formula, MOE represents the desired margin of error (which you set ahead of time), and σ represents the population standard deviation. If σ is unknown, you can estimate it with the sample standard deviation, s, from a pilot study; z* is the critical value for the confidence level you need. Checking Out Statistical Confidence Interval Critical Values Critical values ( z *-values) are an important component of confidence intervals (the statistical technique for estimating population parameters). The z *-value, which appears in the margin of error formula, measures the number of standard errors to be added and subtracted in order to achieve your desired confidence level (the percentage confidence you want). The following table shows common confidence levels and their corresponding z *-values.

Confidence Level z*– value 80% 1.28 85% 1.44 90% 1.64 95% 1.96 98% 2.33 99% 2.58.

Statistics are sets of mathematical equations that are used to analyze what is happening in the world around us. You've heard that today we live in the Information Age where we understand a great deal about the world around us. Much of this information was determined mathematically by using statistics. When used correctly, statistics tell us any trends in what happened in the past and can be useful in predicting what may happen in the future.

One definition of justice is “giving to each what. Everyday human interactions. Encompasses the moral principles which guide us in designing our economic. 10 Everyday Reasons Why Statistics Are Important. Statistics are sets of mathematical equations that are used to analyze what is happening in the world around us.

Let's look at some examples of how statistics shape your life when you don't even know it. Weather Forecasts Do you watch the weather forecast sometime during the day? How do you use that information?

Have you ever heard the forecaster talk about weather models? These computer models are built using statistics that compare prior weather conditions with current weather to predict future weather. Emergency Preparedness What happens if the forecast indicates that a hurricane is imminent or that tornadoes are likely to occur? Emergency management agencies move into high gear to be ready to rescue people.

Emergency teams rely on statistics to tell them when danger may occur. Predicting Disease Lots of times on the news reports, statistics about a disease are reported. If the reporter simply reports the number of people who either have the disease or who have died from it, it's an interesting fact but it might not mean much to your life. But when statistics become involved, you have a better idea of how that disease may affect you. For example, studies have shown that 85 to 95 percent of lung cancers are smoking related. The statistic should tell you that almost all lung cancers are related to smoking and that if you want to have a good chance of avoiding lung cancer, you shouldn't smoke. Medical Studies Scientists must show a statistically valid rate of effectiveness before any drug can be prescribed. Download Advanced Brazilian Jiu Jitsu Techniques Pdf Free.

Statistics are behind every medical study you hear about. Genetics Many people are afflicted with diseases that come from their genetic make-up and these diseases can potentially be passed on to their children.

Statistics are critical in determining the chances of a new baby being affected by the disease. Political Campaigns Whenever there's an election, the news organizations consult their models when they try to predict who the winner is. Candidates consult voter polls to determine where and how they campaign. Statistics play a part in who your elected government officials will be 7.

Insurance You know that in order to drive your car you are required by law to have car insurance. If you have a mortgage on your house, you must have it insured as well. The rate that an insurance company charges you is based upon statistics from all drivers or homeowners in your area. Consumer Goods Wal-Mart, a worldwide leading retailer, keeps track of everything they sell and use statistics to calculate what to ship to each store and when.

From analyzing their vast store of information, for example, Wal-Mart decided that people buy strawberry Pop Tarts when a hurricane is predicted in Florida! So they ship this product to Florida stores based upon the weather forecast.

Quality Testing Companies make thousands of products every day and each company must make sure that a good quality item is sold. But a company can't test each and every item that they ship to you, the consumer. So the company uses statistics to test just a few, called a sample, of what they make. If the sample passes quality tests, then the company assumes that all the items made in the group, called a batch, are good. Stock Market Another topic that you hear a lot about in the news is the stock market. Stock analysts also use statistical computer models to forecast what is happening in the economy.