Thursday HW!

HW, HW, HW....practice is the key to probability! Stay engaged, stay motivated, and work hard--we have to be ready for this test next week!

Thursday's HW: 2 things....

1.) Please complete question 1 on the last slide in our notes (or below)--do this question near the slide in your notebook.

• For this question we're looking at packing two items only, so we only need the "packing" numbers--we won't use the boxing numbers for #1
• Step 1: Find the mean and standard deviation for packing two systems! Look at today's notes about dogs and cats
• Answers: 
• E(packing time for two systems) = 18 min
• St. Dev(packing time for two systems) = 2.12 min
• Step 2: Use your mean and standard deviation for two systems, and the fact that packing times are Normally distributed, to find the probability it takes over 20 minutes to pack 2 systems!
• Normalcdf!
• Be sure to show a shaded model and normalcdf with each value labeled

2.) Please complete the following in your textbook:

• Page 383: 25, 27ab, 31bc
• 25 uses some of the ideas of rescaling with combining random variables...
• For example, look at #26:
• 26a.) 2Y + 20
• E(2Y + 20) = 2(12) + 20 = 44
• St. Dev(2Y + 20) = 2(3) = 6 (we don't add 20 because shifting doesn't affect st. dev)
• 26c.) 0.25X + Y
• E(0.25X +Y) = 0.25(80) + 12 = 32
• St. Dev(0.25X + Y)
• First, find the st. dev for 0.25X = 0.25(80) = 20
• From here, we can't add standard deviations...variances always add, so we do 20^2 + 3^2 = 409. 409 is the variance, so st. dev. = sqrt(409) = 20.223
• 27ab and 31bc are more like the dogs/cats examples from our notes today

If you were out today here are the notes from our slides about cats and dogs:

And here is the slide for the homework question:

Lastly, many people have been asking if we'll have work over break....kinda/maybe...

• Our next unit when we come back from break is about how to collect data; you will have to read chapter 13 (experiments and observational studies), take notes/answer questions based on your reading, and then complete a multiple choice packet--this will all be on your own
• This assignment will be due the Tuesday after 3 Kings Day (1/7)
• I will post the assignment on the blog, so if you want to do it over break, you can (and then not stress that 3 day weekend)
• Or, if you want to just enjoy the break, you can save all this for the 3 day weekend...your call.