Given Information:
Mean weekly salary = μ = $490
Standard deviation of weekly salary = σ = $45
Required Information:
P(X > $525) = ?
Answer:
P(X > $525) = 21.77%
Step-by-step explanation:
We want to find out the probability that a randomly selected teacher earns more than $525 a week.

The z-score corresponding to 0.78 from the z-table is 0.7823

Therefore, there is 21.77% probability that a randomly selected teacher earns more than $525 a week.
How to use z-table?
Step 1:
In the z-table, find the two-digit number on the left side corresponding to your z-score. (e.g 0.7, 2.2, 1.5 etc.)
Step 2:
Then look up at the top of z-table to find the remaining decimal point in the range of 0.00 to 0.09. (e.g. if you are looking for 0.78 then go for 0.08 column)
Step 3:
Finally, find the corresponding probability from the z-table at the intersection of step 1 and step 2.
Answer:
The total percent decrease is 
Step-by-step explanation:
- We are given with a word problem
- We are asked to find the total percentage decrease
- We can do this in two steps
Step 1: Finding the two percentage decrease
Step 2: Finding their difference
Step 1 of 2
Let the decrease by a% be 100-a
Then b% decrease is

Step 2 of 2
The percentage difference between the two percentages is,

Since 100 is the total percent
is the percentage decrease.
Answer:
The correct option is 1.148 < σ < 6.015
Explanation:
The 99% confidence interval for the standard deviation is given below:

Where:


Therefore, the 99% confidence interval is:


Therefore, the option 1.148 < σ < 6.015 is correct
Answer:
33%
Step-by-step explanation:
4.90*0.33=1.617
1.617+4.90=6.517≈6.50