Introduction to Applied Statistics

In general, what would a researcher prefer in order to collect the most accurate data - an observational study or an experiment? Why?

An experiment. That way the researcher can assign the treatments themselves, employ randomness, and ultimately make causal conclusions between treatment(s) and response.

Suppose a researcher wishes to study and track the behavior of known bank robbers - such as which banks they target, what time of day they perform the robbery, whether or not they use force, etc. In order to collect data, would the researcher have to employ an observational study or would they be able to run a true experiment? Why?

An observational study. Performing an experiment here would likely be very dangerous and is certainly unethical. This demonstrates that some experiments just aren't feasible even if they would bring in the best data.

A scatterplot indicates a positive association between two variables: tree height and trunk circumference. Which statement is true about this association?

As tree height increases, trunk circumference increases.

Data were collected from a statistics course on campus. The variables that were recorded for each student are: the number of students that were driving home after class and the speed at which they were driving. Classify the variable of speed at which they were driving home.

Continuous numerical

Data were collected from consumers at a local grocery store. The variables that were recorded for each consumer: number of purchases in last 30 days and amount of purchase. Classify the number of purchases in last 30 days variable.

Discrete numerical

A variable that might have an effect on another variable is called a(n) ____ variable.

Explanatory

True or false? The explanatory and response variables can be independently associated?

False

Suppose we are conducting a detailed survey to determine the differences in how men and women discipline their children. Which type of sampling method makes the most sense here, and why?

Stratified Sampling - it ensures we obtain a certain amount of both men and women in our sample. Another sampling method may result in a disproportionate amount of one gender.

A scatterplot shows a negative association between two variables. What is the best description of this graph?

The points plotted indicate a downward trend.

True or False: A sample is referred to as "simple random" if each case in the population has an equal chance of being included in the final sample and each case is independent from the other cases.

True