Bias and Sampling
This sampling method is easy to do and leads to biased data.
What is convenience sampling?
The sum of all probabilities in a sample space equals this value.
What is 1?
This measure of spread is found by subtracting the minimum from the maximum.
What is range?
These are the three factors of experimental design.
What are control, randomization, and replication?
This symbol can be used to store a matrix/list/variable.
What is the Store function/[CTRL] + [VAR]?
This is a type of sampling where a population is divided into subgroups, and then random samples are selected from each group.
What is stratified sampling?
Given that two events are independent, this is how you can determine the probability that both of them will occur.
What is multiply their probabilities?
This term describes a kind of distribution with two clear peaks.
What is bimodal?
Sally is planting 16 tomatoes. 8 are planted in 1 of 2 types of soil, and the other 8 are planted in the other type. One type is the standard soil she usually uses, and the other has additional fertilizer. She wants to test the efficacy of this fertilizer. This is the controlled variable.
What is addition of fertilizer?
This is the difference between Cdf and Pdf.
What is Cdf focuses on a range of outcomes, and Pdf only considers one outcome?
A scientist wants to collect data on a homogenous population. This is the most appropriate sampling method (aside from SRS).
What is cluster sampling?
A student surveys his 120 classmates about what clubs they are in. 50 are in the sports club, 40 are in the music club, and 18 are in both the sports and music club. This is the probability that a randomly selected student is in the sports club given they are in the music club.
What is 9/20 or 0.45?
P(S|M) = P(S∩M)/P(M) = (18/120)/(40/120)
The median represents this percentile of a data set.
What is the 50th percentile?
A group of researchers conducts an experiment where randomly selected volunteers are given a new medicine, or a placebo. The volunteers don’t know which one they have been given, and the scientists conducting observations also do not know. This is the kind of experiment this is.
What is double blind?
This is how you can find the critical value of a normal distribution using a calculator function.
What is invNorm (inverse Norm)?
A manager asks employees in the workplace about their opinion on the company’s employee benefits. The manager sends the people in their department a survey. These are some potential biases.
What is survey bias, nonresponse/voluntary response bias, undercoverage?
This is what P(A | B) * P(B) is equivalent to.
What is P(A ∩ B)?
This type of graph is best for identifying outliers and determining IQR.
What is a boxplot?
Dorisa is testing the efficacy of different detergent brands. She washes one batch of colorful clothes with brand A in cold water, and then another batch of white clothes with brand B in warm water. These are the confounding variables.
What are clothing color and water temperature?
This is how you access the expected values matrix after using a chi-square test.
What is press var and select stat.expectedVal?
Suppose a car insurance agent is trying to determine how many customers are satisfied with the current price of their insurance plan. The agent decides to hand out optional surveys to the customers who walk into the store, and records the responses of the surveys he gets back. These are the sampling method and the possible biases present in this experiment.
What are convenience sampling, voluntary response bias, survivorship bias?
A professor discovers that 40% of his students are women, and 60% are men. 25% of the women do not like mint chocolate ice cream, and 30% of the men do like mint chocolate. This is the probability that a randomly selected student is a man given they do not like mint chocolate ice cream.
What is 0.808?
P(M|~C) = P(M∩~C)/P(~C) = .42/0.52 = 0.808
P(M) = 0.6, P (~C) = .4*.25 + .6*.7 = 0.52
P(M∩~C) = .6*.7 = 0.42
If the mean is higher than the median, this feature is likely present.
What is Right skewness OR high outliers?
Jonathan is tasked with determining if a brand of roller skates new to the market has a higher average speed than the current brand of skates that he sells. He buys 10 of the new brand roller skates and rides them down the same hill, twice for each pair of skates. These are the mistakes Jonathan made in his experiment.
What is did not randomly select units, did not make control group?
Sophia is conducting a 95% two-sided confidence interval. She needs to find the t* value with inverseT. This is the value she should use as the area.
What is 0.975?