SOCR EduMaterials Activities Distributions

SOCR Educational Materials - Activities - SOCR Computing Probabilities Activity

Goal: Using SOCR to compute probability for different distribution.

Address: http://socr.stat.ucla.edu/htmls/SOCR_Distributions.html

Example: Here we use normal distribution (mean=5, sigma=4) as an example.

Step 1: Set up parameters. Select the Normal Distribution from the drop-down list on the top-left. Set Mean = 5 Standard Deviation = 4

            Now the density function of normal (mean=5, sigma=4) will show up in the top-right with red color. See following figure.

Step 2: Compute P(X<7) Move cursor from 21, the most right side, to the right until 7. Now the red area means X<7. And the probability of red area is always represented by the value of “Between”. Hence P(X<7)=0.69. See attached figure.

To get a snapshot of this result, click on snapshot. Then save the file with a filename and extension .jpeg , for example, hwk1-parta.jpeg. When done, you can open that new .jpeg file and go to edit-> copy.. Open separately a Word file and paste into that file. You can reduce the image, but make sure that it is big enough for us to see the numbers

Step 3: Compute P(X>3) Move cursor from -11, the most right side, to the left until 3. Red area means X>3. And the probability of red area is always recorded in the value of “Between”. Therefore, P(X>3)=0.69. See attached figure.

Step 4: Compute P(2<X<6)

First, move cursor from -11, the most left side, to the right until 2. Then move cursor from 21, the most right side, to the left until 6. Find “Between” in the bottom-right widow, which is just the probability of red area. Then P(2<X<6)=0.375. See attached figure.

Similarly, we can use SOCR to compute the probability in other known distribution, such as uniform distribution, exponential distribution.

• SOCR Home page: http://www.socr.ucla.edu

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