DISTRIBUTION (การแจกแจง)

The fx-991EX can generate probability distribution tables, covering Normal, Inverse Normal, Binomial, and Poisson distributions.

From the main menu, use the arrow keys to highlight the Distribution icon and press EXE or press 7.

The distribution options will appear. Use the arrow keys to navigate to the second page.

Distribution Options

• 1: Normal PD
• 2: Normal CD
• 3: Inverse Normal
• 4: Binomial PD

Select 1 (Binomial CD) from the second page to analyze problems related to the binomial distribution. For example: "When rolling a fair six-sided die 6 times, what is the probability of rolling a 6 at least twice?"

To input the values for x (number of successes), N (number of trials), and p (probability of success), press 2 (Variable). Input the values as shown, using the fraction symbol to separate numerator and denominator.

After inputting the values, pressing EXE will automatically convert the fraction to a decimal. Press EXE again to calculate the probability.

The probability of 73.7% will be displayed. If you input x = 1, the calculator will compute P(≤ 1 roll of a 6 in six throws), which is more likely to be calculated using the complement of the event: P = 1 - 0.737 = 0.263 = 26.3%.

To display the probability of obtaining any number in six rolls of a die, press OPTN 1 (Select Type).

Now, select 4 (Binomial PD).

If calculating probabilities for multiple different numbers of successes, select 1 (List).

Input the numbers 0, 1, 2, 3, 4, 5, and 6 into the "x" column (representing the number of successes). Press EXE after each input.

After the last input, press EXE again to finalize the data entry process.

Note that the values for N and p are retained from the cumulative probability calculation (N and p are universal calculator variables).

Press EXE again to calculate the probability distribution table.

Observe that probabilities of less frequent events are displayed in scientific notation!

INVERSE NORMAL

To calculate the inverse normal distribution, press OPTN 1 (Select Type).

(Editor) will edit the previous PD data entries.

Select 3 (Inverse Normal).

Input the values to answer the question: "If the heights of American men are normally distributed with a mean of 70 inches and a standard deviation of 4 inches, what range represents the tallest 10% of American men?"

Press EXE again to display the results. To be in the tallest 10% of American men, a man must be taller than 75 inches (6'3").