STA1101 Normal Distribution and Continuous random variables
Continuous Random Variables
A random variable whose values are not countable is called a continuous random variable.
The Normal Distribution
The normal probability distribution is given by a bell-shaped(symmetric) curve.
The Standard Normal Distribution
The normal distribution with
Example 1: Find the area under the standard normal curve
between z = 0 and z = 1.95
from z = -2.17 to z = 0
Area to the right of z = 2.32
Area to the left of z = -1.54
Example 2a: Find the following probabilities for the standard normal curve.
Example 2b: Find the value of k if
Standardizing A Normal Distribution
Example 3: Let x be a normal random variable with its mean equal to 40 and standard deviation equal to 5. Find the following probabilities for this normal distribution.
Example 4: Lengths of metal strips produced by a machine are normally distributed with mean length of 150cm and a standard deviation of 10cm.
Find the probability that the length of a randomly selected strip is
(a) shorter than 165cm,
(b) within 5cm of the mean.
Example 5: The time taken by the milkman to deliver to the High Street is normally distributed with a mean of 12 minutes and a standard deviation of 2 minutes. He delivers milk every day. Estimate the number of days during the year when he takes
(a) longer than 17 minutes,
(b) less than ten minutes,
(c) between 9 and 13 minutes.
Example 6: The height of female students at a particular college are normally distributed with a mean of 169cm and a standard deviation of 9 cm.
(a) Given that 80% of these female students have a height less...