A zscore is a common way to standardize a set of statistical data. Statisticians, business people, scientists and market analysis use zscores to help them find the point that a piece of data would be found in a normal distribution. A 98 percent zvalue indicates very high confidence that the result is not random.

Use the zscore formula to solve for the 98 percent confidence. The formula is zscore = (x  mean) / sigma.
In the formula, x is the data point, mean is the average of the numbers and sigma is the standard deviation of the numbers in your data set.

Find the zvalue by plugging in the numbers. If x is 10, the mean is 5 and sigma is 2.3, then the z value is z = (10  5) / 2.3. Solving determines that z = 2.17.

After finding the zvalue is 2.17, look up the conversion on a zvalue table in a book or online. Using the table, it is learned that the zvalue is 98.4996. This falls above the 98 percent confidence threshold that was set, so it is accepted. In other words, there is a 98 percent confidence that the number 10 could be found in the data.
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