It is the distribution that occurs when a normal random variable has a mean of zero and a standard deviation of one. The standard normal distribution is a special case of the normal distribution. Thus, about 68% of the test scores will fall between 90 and 110. We use these findings to compute our final answer as follows: To compute P( X We use the Normal Distribution Calculator to compute both probabilities on the right side of the above equation. The "trick" to solving this problem is to realize the following: Solution: Here, we want to know the probability that the test score falls between 90 and 110. If the test has a mean of 100 and a standard deviation of 10, what is the probability that a person who takes the test will score between 90 and 110? Suppose scores on an IQ test are normally distributed. Hence, there is a 90% chance that a light bulb will burn out within 365 days. We enter these values into the Normal Distribution Calculator and compute the cumulative probability.
How to call the function normalcdf()?įollow the path below to call the command. There is a command in TI84 named 2: normalcdf() to find normal probabilities. We can use the following procedure to find p-values as well. Finding a p-value is the same as finding normal probability for the given test statistic. While using the Z test we need to find the p-value for making decisions. In this situation, we use standard normal distribution or Z distribution hence we call it as Z test.
In hypothesis testing, we use the normal distribution to test the claim about population mean (µ) if we know population standard deviation (σ) prior. Use of TI84 calculator to find normal probabilities