This app lets you study different probability distributions such as Binomial, Normal or Exponential. Input the distribution’s parameters and get the corresponding probabilities. It is organized in 3 steps:

- Choice of probability distribution: select the probability distribution you want to perform your probability calculations, the normal distribution for example.
- Choice of the parameters: type the values of the parameters of the probability density function, standard deviation and mean for example.
- Calculate probabilities: define your bounds and calculate the corresponding probability or perform the inverse by typing a probability value to calculate the value of the corresponding bound.

Once you have made a choice and moved to the next step, you can return to the previous step by pressing **BACK**.

Select the probability distribution you want with the directional arrows. Then confirm by pressing **OK** to go to the next step.

You have the choice between 3 continuous distributions and 2 discrete distributions.

Continuous distributions:

- Uniform distribution
- Exponential distribution
- Normal distribution

Discrete distributions:

- Binomial distribution
- Poisson distribution

Type the value of the parameter(s) then select the **Next** button and press **OK** to go to the next step.

At the bottom of the screen, you will see a description of the requested parameters.

In the table below, the parameters requested for each distribution are reminded.

Probability distribution | Requested parameters | What value to enter |
---|---|---|

Binomial | ($n$, $p$) : number of trials and success probability | (natural number, real number in $[0,1]$) |

Uniform | ($a$, $b$): bounds of the interval | (real number, real number) |

Exponential | $\lambda$: parameter | non-negative real number |

Normal | ($\mu$, $\sigma$): mean and standard deviation | (positive real number, non-negative real number) |

Poisson | $\lambda$ :parameter | non-negative real number |

- Select the bound in which you want to enter your value.
- Type the value.
- Confirm by pressing
**OK**.

You can now read the result of the probability calculation.

You can modify the type of bounds for your probability calculations:

- $X≤a$
- $a≤X$
- $a≤X≤b$
- $X=a$

The last option only concerns discrete distributions.

To do so, follow the instructions below.

- Select the
**Bound type**icon at the top left of the screen and press**OK**. - A drop-down menu opens. Choose the type of bounds you want and confirm by pressing
**OK**.

You have changed the type of bounds for calculating your probabilities.

You can calculate $a$ in $P(a≤X)=p$ from a given $p$ probability value.

- Select the field in which the probability value is located.
- Type your value.
- Confirm by pressing
**OK**.

The calculator will display the value of $a$.