Probability
If P(X) has a probability of (0.7), what is the probability that the event does not occur p(Xc)?
P(Xc)= 0.3
A researcher wants to estimate the average amount of sleep high school students get per night using a random sample. Which inference procedure should they use?
One-sample t-interval for population mean
A researcher wants to survey students at a school. She randomly selects 50 students ID numbers from the school database. What sampling method is this?
Simple random sample
Which measure of center is more resistant to outliers: median or mean?
The median
What are the four characteristics to include when describing a scatter plot.
direction, linear, strength, and unusual features
What is the probability of rolling a number greater than 4 on a six-sided die?
2/6
A company claims its batteries last an average of 18 hours. A random sample of 20 batteries is tested to determine whether the true mean lifetime is actually lower. Which inference procedure would you use?
One sample t-test
A scientist divides a population into males and females, then randomly samples from each group. What sampling method is being used?
Stratified random sample
A distribution has a mean of 45 and a standard deviation of 5. A value of 60 has what z-score?
z=3
Events that can not happen at the same time are called?
mutually exclusive
A basketball player makes 85% of free throws. Find the probability that she misses at least one of the 2 free throws?
P(At least one miss)= 1-(.85)2 =1-.7225
P(At least one miss)= .2775
A doctor compares blood pressure before and after patients begin a new medication. Each patient is measured twice. Which inference procedure would you use?
Matched pairs t-test
A school principal surveys the first 30 students who arrive at school. What type of sampling method is this?
Convenience sample
A box plot has Q1=12 and Q3=24. According to the 1.5(IQR) rule, what values are considered outlier on the high end?
Any values greater than 42
The Null Hypothesis Ho: The new drug is equally as effective as the placebo.
Alternative Hypothesis Ha: The new drug is more effective than the placebo.
Explain the meaning of a Type I Error in context.
A Type I Error occurs when you reject a true null hypothesis. A Type I Error means that the new drug is more effective than the placebo when it is actually not more effective.
The probability a customer buys dessert is .4. Find the probability more than 6 customers buy dessert
Geometric, P(X)= .4
=.953
Two brands of batteries are tested to compare average battery life. Fifty batteries from each brand are randomly selected and tested independently. Which inference procedure would you use?
Two-sample t interval
A researcher randomly selects 5 random classrooms and surveys every student in those classrooms. What sampling method is this?
Cluster sample
A dataset is strongly skewed right with several high outliers. Which measures of center and spread are most appropriate?
Median and IQR
You are analyzing the average price of gas in your town. You randomly sample (8) gas stations and record the prices: ($2.13, $2.10, $1.80, $2.09, $2.17, $2.12, $2.10, $2.11).Have all conditions and assumptions for inference been met? Why not if so?
No they have not been met because sample size is only (n = 8). For quantitative data (like gas prices), we either need to know the population is Normal or our sample size needs to be larger (n>30) to rely on the Central Limit Theorem.
A test for a disease is 96% accurate for sick people and 92% accurate for healthy people. If 5% of the population has the disease, find the probability of a randomly selected person tests positive.
P(positive)=(.96)(.05)+(.08)(.95)
P(positive )= .124
A study compares the proportion of drivers who text while driving in two different states. Which inference test should be used?
Two sample z-test for proportions
A study uses volunteers who can choose to respond to the survey about homework stress. What type of bias is present?
Voluntary response bias
A distribution is symmetric with no outliers. The mean is 52 and a standard deviation of 3. If every value in the dataset is multiplied by 4, what will the new mean and standard deviation be?
Mean=208
SD=12
A 95% confidence interval for a population mean is (12,18). Interpret the interval.
We are 95% confident the true population mean is between 12 and 18