AP STATS Review #4_SEM1

A certain type of bird lives in two regions of a state. The distribution of weight for birds of this type in the northern region is approximately normal with mean 10 ounces and standard deviation 3 ounces. The distribution of weight for birds of this type in the southern region is approximately normal with mean 16 ounces and standard deviation 2.5 ounces.

What is the weight of a bird in the southern region whose weight is in the 65th percentile?

(Round to the nearest whole number)

Answer explanation

Use stapplet, click normal distribution and select the option for calculating a value. Enter the appropriate information.

A random sample of 2,500 people was selected, and the people were asked to give their favorite season. Their responses, along with their age group, are summarized in the two-way table below.

Among those whose favorite season is spring, what proportion are adults?

• $\frac{250}{1000}$

• $\frac{250}{2500}$

• $\frac{475}{2500}$

• $\frac{250}{475}$

• $\frac{225}{475}$

Answer explanation

This type of problem is an example of conditional relative frequency.

Tags

CCSS.8.SP.A.4

A certain store has 3,000 employees working at its main location in a city and 100 employees working at a smaller location outside the city. The store manager will select a sample of 50 employees from all the employees to ask their opinions about extending store hours during the holidays. What is the advantage of selecting a stratified random sample, with location as strata, instead of a simple random sample?

• The stratified sample assures the most random selection from among all selection methods.

• The stratified sample assures that the opinions of employees from both locations will be represented.

• The stratified sample will be less expensive to implement than a simple random sample and will save money over time.

• The stratified sample assures employees that store hours will not be extended until their opinions are recorded.

• There is no real advantage to stratifying because a simple random sample is always the best.

Answer explanation

Other sampling methods could result in underrepresentation of the opinions of the 100 employees at the smaller location. The use of a stratified sample ensures that the opinions of the employees at both locations will be considered.

Tags

CCSS.HSS.IC.B.3