Percentile Values
1. **Problem Statement:**
A) Find the 14th percentile (P14) for the standard normal distribution $Z$.
B) Find the 95th percentile (P95) for the $t$-distribution with 12 degrees of freedom ($t_{12}$).
2. **Formulas and Important Rules:**
- The percentile $P_p$ is the value below which $p\%$ of the data falls.
- For the standard normal distribution $Z$, percentiles correspond to $z$-scores found using the inverse cumulative distribution function (CDF).
- For the $t$-distribution with $df$ degrees of freedom, percentiles correspond to $t$-scores found using the inverse CDF of the $t$-distribution.
3. **Step A: Find $P14$ for $Z$**
- We want $z$ such that $P(Z \leq z) = 0.14$.
- Using standard normal tables or a calculator, find $z = \Phi^{-1}(0.14)$.
- From tables or software, $z \approx -1.080$ (rounded to 3 decimals).
4. **Step B: Find $P95$ for $t_{12}$**
- We want $t$ such that $P(T \leq t) = 0.95$ with $df=12$.
- Using $t$-distribution tables or software, find $t = t_{0.95,12}$.
- From tables or software, $t \approx 1.782$ (rounded to 3 decimals).
**Final answers:**
- $P14$ for $Z$ is approximately **$-1.080$**.
- $P95$ for $t_{12}$ is approximately **$1.782$**.
These values represent the cutoff points below which 14% and 95% of the respective distributions fall.