CONFIDENCE INTERVAL MINITAB 17 HOW TO
Here is how to find calculate the 90% confidence interval for the true population mean weight:ĩ0% Confidence Interval: 300 +/- 1.645*(18.5/√25) = The following table shows the z-value that corresponds to popular confidence level choices: Confidence Levelįor example, suppose we collect a random sample of turtles with the following information: The z-value that you will use is dependent on the confidence level that you choose. This formula creates an interval with a lower bound and an upper bound, which likely contains a population parameter with a certain level of confidence.Ĭonfidence Interval = įor example, the formula to calculate a confidence interval for a population mean is as follows: It is calculated using the following general formula:Ĭonfidence Interval = (point estimate) +/- (critical value)*(standard error) A confidence interval is a range of values that is likely to contain a population parameter with a certain level of confidence. In order to capture this uncertainty we can create a confidence interval.
CONFIDENCE INTERVAL MINITAB 17 FULL
For example, we might just happen to pick a sample full of low-weight turtles or perhaps a sample full of heavy turtles. The problem is that the mean weight of turtles in the sample is not guaranteed to exactly match the mean weight of turtles in the whole population. Instead, we might take a simple random sample of 50 turtles and use the mean weight of the turtles in this sample to estimate the true population mean: Since there are thousands of turtles in Florida, it would be extremely time-consuming and costly to go around and weigh each individual turtle. Instead, we typically take a random sample from the overall population and use data from the sample to estimate the population parameter.įor example, suppose we want to estimate the mean weight of a certain species of turtle in Florida. the proportion of residents in a county who support a certain law)Īlthough we’re interested in measuring these parameters, it’s usually too costly and time-consuming to actually go around and collect data on every individual in a population in order to calculate the population parameter. the mean height of males in the U.S.)Ģ. Population proportion: the proportion of some variable in a population (e.g. Population mean: the mean value of some variable in a population (e.g. Two of the most common population parameters are:ġ. Often in statistics we’re interested in measuring population parameters – numbers that describe some characteristic of an entire population.
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