What is the 95th percentile of a normal curve?
When we go to the table, we find that the value 0.90 is not there exactly, however, the values 0.8997 and 0.9015 are there and correspond to Z values of 1.28 and 1.29, respectively (i.e., 89.97% of the area under the standard normal curve is below 1.28)….Computing Percentiles.
| Percentile | Z |
|---|---|
| 90th | 1.282 |
| 95th | 1.645 |
| 97.5th | 1.960 |
| 99th | 2.326 |
How to calculate percentiles of a normal distribution?
In some instances it may be of interest to compute other percentiles, for example the 5 th or 95 th. The formula below is used to compute percentiles of a normal distribution. where μ is the mean and σ is the standard deviation of the variable X, and Z is the value from the standard normal distribution for the desired percentile.
Which is the best way to calculate percentiles?
The standard normal distribution can also be useful for computing percentiles. For example, the median is the 50 th percentile, the first quartile is the 25 th percentile, and the third quartile is the 75 th percentile. In some instances it may be of interest to compute other percentiles, for example the 5 th or 95 th.
How to find the 90 th percentile in probability?
To compute the 90 th percentile, we use the formula X=μ + Zσ, and we will use the standard normal distribution table, except that we will work in the opposite direction. Previously we started with a particular “X” and used the table to find the probability.
How to calculate the 90 th percentile of BMI?
The 90 th percentile is the BMI that holds 90% of the BMIs below it and 10% above it, as illustrated in the figure below. To compute the 90 th percentile, we use the formula X=μ + Zσ, and we will use the standard normal distribution table, except that we will work in the opposite direction.