Unit 2 check

Unit 2 check: Probability, Random Variables, and Probability Distributions

12 questions from 12 lessons in Unit 2. Answer each one, and if you miss, follow the link back to where it is taught, then try again. Your score counts first tries.

Question 1 · from 2.1 · Multiple choice

A segmented bar chart shows how the students in each grade at a high school get to school: walking, bus or car. Which feature of the chart would show that grade and travel method are not associated?

Question 2 · from 2.2 · Multiple choice

Use the same survey: 27 of the 90 voters under 35 and 72 of the 160 voters aged 35 or older plan to vote early. Which calculation gives the conditional relative frequency of planning to vote early among voters aged 35 or older?

Question 3 · from 2.3 · Calculate

A driver's route to work has 4 traffic lights. A student simulated 500 drives and recorded how many red lights the driver hit: 0 red lights in 41 drives, 1 in 137, 2 in 182, 3 in 109 and 4 in 31. Use the simulation to estimate the probability that the driver hits at most 1 red light. Give a decimal.

Your answer

Question 4 · from 2.4 · Multiple choice

A student says: "Flip two fair coins and there are three possible results: two heads, two tails, or one of each. So the probability of one of each is $\frac{1}{3}$ ." What is wrong with this reasoning?

Question 5 · from 2.5 · Multiple choice

A survey of 300 students found that 80 are in the band, 120 play a sport and 45 do both. One of these students is chosen at random. Which statement gives the correct decision about whether "in the band" and "plays a sport" are mutually exclusive, with a valid reason?

Question 6 · from 2.6 · Calculate

Of 320 juniors at a school, 96 have a part-time job. Of 280 seniors, 140 have one. One of these 600 students is chosen at random. Given that the student has no job, what is the probability that the student is a junior? Round to three decimal places.

Your answer

Question 7 · from 2.7 · Calculate

A forecast gives a 30% chance of rain on Saturday, a 40% chance of rain on Sunday, and a 15% chance of rain on both days. What is the probability that it rains on at least one of the two days? Give a decimal.

Your answer

Question 8 · from 2.8 · Multiple choice

The number of siblings X of a randomly chosen student at a school has this cumulative distribution:

\begin{matrix} x & 0 & 1 & 2 & 3 \\ P (X \leq x) & 0.20 & 0.55 & 0.85 & 1 \end{matrix}

What is $P (X = 2)$ ?

Question 9 · from 2.9 · Multiple choice

A bakery counts its wedding cake orders each week. The number of orders in a week, X, has $μ_{X} = 1.75$ and $σ_{X} \approx 1.18$ . Which is the best interpretation of the standard deviation?

Question 10 · from 2.10 · Multiple choice

A delivery company claims that 90% of its packages arrive on time. You track 20 randomly chosen packages, and only 14 arrive on time. Assume packages arrive on time independently. If the claim is true, $P (X \leq 14) \approx 0.011$ . What does this suggest?

Question 11 · from 2.11 · Multiple choice

Two normal curves have the same mean. Curve A has standard deviation 5 and curve B has standard deviation 10. Which statement is true?

Question 12 · from 2.12 · Multiple choice

The amounts customers spend at a hardware store are skewed to the right. A manager takes many random samples of 100 receipts and computes the mean of each sample. Which best describes the distribution of those sample means?

0 of 12 answered.