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Title screen: How tu use Binom.dist. Copyright ©2017 McGraw-Hill Education. All rights reserved.
Narrator: "In this video, we will demonstrate how to apply the BINOME. DIST formula in Excel to calculate discreet and cumulative probabilities based on the binomial probability distribution. In this example, we have a new acne medication which is claimed to be 80% effective. A sample of 15 people are using the medication. In the first case, we are asked to determine the probability that all 15 participants will see significant success from using the medication. The BINOME. DIST function in Excel makes it easy to solve this type of probability. But it is critical to know all the variables that go into the function. I've pasted in an image of the dialogue box."
The Function Arguments dialog box contains fields for Number s, Trials, Probability s, and Cumulative. Text is overlaid in each field: Number s, number of successes; trials, number in the sample; probability s, probability of success; cumulative, true equals cumulative.
Narrator: "Let's go through the first question and walk through the dialogue box. =BINOME. DIST(, and then clicking the Fx button."
Equals Binome dot dist left parenthesis is entered into cell H5. The F x button, left of the formula bar above the sheet, is clicked to open the Function Arguments dialog box and to close the parentheses of the formula.
Narrator: "Let's go through the first question, and walk through using the dialogue box. Our first question asks for the probability that all 15 participants in the sample will show significant improvement. We are therefore looking for the probability that the number of successes equals 15. Number(underscore)S is the number of successes we want to determine the probability for. In this case, that would be 15. Trials is the number in our sample. In this case, that's also 15. Probability(underscore)S means the probability of success, which is believed to be 80%. You can enter . 8 or you can enter 80%. Cumulative can either be set to TRUE or FALSE. If I enter TRUE, it means I want the probability up to and including that number of successes."
Text: True equals P left parenthesis x right parenthesis less than or equal to some value.
Narrator: "FALSE means I want the probability of getting exactly that number of successes. For this problem, I would therefore set cumulative equal to FALSE, because we are looking for the probability of exactly 15 successes. Once I enter FALSE, the answer shows in the dialogue box."
The answer is displayed below the text fields and within cell H5.
Narrator: "I'll go ahead and click 'Okay,' and we see .035, or 3.5%, is the probability that all 15 participants will see significant improvement by using the new acne medication if it has a probability of success of 80%. The next problem asks for the probability that fewer than 9 of 15 will show improvement."
Text: P left parenthesis x right parenthesis less than nine is the same as P left parenthesis x right parenthesis less than or equal to eight.
Narrator: "In this case, we care whether one or two or three or up to eight people, but not nine, show improvement. This is a 'cumulative equals TRUE' problem. This time, instead of the dialogue box, let's enter the formula directly in the cell. =BINOME. DIST( —and it tells us first enter the number of successes that you care about."
As the open parenthesis is entered, a box appears below the cell indicating the values that should be entered to the formula: number s, trials, probability s, and cumulative.
Narrator: "And I will enter eight, because we care about less than nine. Next, I'll enter 15 for the number of items in our sample, which is also considered the number of trials. The probability is .80, and I'll set this to be TRUE. Close parenthesis and hit 'Enter.'"
The full formula in cell H6: equals binom dot dist left parenthesis eight comma 15 comma point 80 comma true right parenthesis.
Narrator: "The probability is just under 2% that fewer than nine people will show significant improvement. And, finally, what is the probability that 12 or more will show improvement? When we use cumulative equals TRUE, Excel returns the probability of 'X' less than or equal to some number of successes. We need a way to determine greater than or equal to. For that, we can use 1 minus the BINOME. DIST formula, setting cumulative equal to TRUE. These are whole-number variables, therefore if use 1 minus the probability of 11 or fewer successes, we would find the probability of 12 or more successes."
Text: One minus P left parenthesis x right parenthesis less than or equal to 11 is the same as P left parenthesis x right parenthesis greater than or equal to 12.
Narrator: "Equals 1 minus BINOME. DIST. My number of successes here is 11, because we're going to set cumulative to be TRUE, which will tell me the results of up to and including 11. 0.8 for the probability, and TRUE. Close parenthesis."
The formula in cell H7: equals 1 minus binom dot dist left parenthesis 11 comma 15 comma point eight comma true right parenthesis.
Narrator: "And the probability is just under 65% that 12, 13, 14, or 15 will show significant improvement. In this video, you have learned how to apply the BINOME. DIST formula to determine discreet and cumulative probabilities using a binomial probability distribution."
Video has ended.
Described transcript ©2023 McGraw Hill. All rights reserved. No reproduction or further distribution permitted without the prior written consent of McGraw Hill.
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