Since the mean indicates the average value of a sample or population of data, you can find your standard measurement using the AVERAGE function. Typically, you are given the mean and SD values from the start, but if that’s not the case, you can easily compute these values in just a few simple steps. Getting Startedįor illustration purposes, let’s assume you have the test scores of 200 students and want to grade them “on a curve,” meaning the students’ grades will be based on their relative performance to the rest of the class: Now that you know the essentials, let’s move from theory to practice. It’s worth mentioning the 68-95-99.7 rule that can be applied to any normal distribution curve, meaning roughly 68% of your data is going to be placed within one SD away from the mean, 95% within two SD, and 99.7% within three SD. The lower the SD, the taller the curve and the less your data will be spread out, and vice versa. For instance, in the bell curve shown above, one standard deviation of the mean represents the range between exam scores of 53 and 85. ![]() This defines the spread of your data in the normal distribution-or in plain English, how wide the curve should be.
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