#### Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

#### CFA Events Calendar

View full calendar

#### CFA Events Calendar

View full calendar

#### Recommended Discussions

See how our partners can help you ace your CFA exams.

# Common Probability distribution

OklahomaPosts: 24 Associate

Hello- Need help with this question please. I am not sure where the answer is 3.59%.

Thank you for taking a look in advance.

Cumulative z-table:

z 0.00 0.01 0.02 0.03

1.6 0.9452 0.9463 0.9474 0.9484

1.7 0.9554 0.9564 0.9573 0.9582

1.8 0.9641 0.9649 0.9656 0.9664

Monthly sales of hot water heaters are approximately normally distributed with a mean of 21 and a standard deviation of 5. What is the probability of selling 12 hot water heaters or less next month?

I picked 0.9641. i was wrong. it is 3.59% (Where did they calculate 3.59%)

• Dallas,TXPosts: 17 Associate

You were close to getting this one.

Short version is you needed to do 1-0.9641 = 0.0359

96.41% represents the probabilty of selling 12 hot water heaters or MORE. The question calls for 12 or Less.

Always best to draw graphs on these to give yourself a visual.

• OklahomaPosts: 24 Associate

OMG. 🤦‍♀️

I truly appreciate your help.