Lesson: Collecting Data

Chapter 1

Collecting Data

Why Statistics?

Take a look at chart a to the right:

• What does it show you?
• What can you learn from it?
• What does it seem to say about the two

variables?

We’re presented data like this to give us
information everyday. We can learn a lot by
observing data and interpreting the results
of studies.

But can we always depend on the results?

Reading Datasets

What are the cases?

What are the variables?

What does this table tell us about the individuals taking the survey?

What variables are Categorical?

Which are Quantitative?

Here’s a dataset giving information about select movies
from 2011.

What are the cases?

What are the variables?

Which variables are Categorical? Which are Quantitative?

Multiple Choice

Where do you plan on attending college?

• Categorical

• Quantitative

Multiple Choice

Which of the following is an example of categorical data?

• High School Graduate or Not

• Annual Income

• Years of Schooling Completed

• Years of playing an instrument

Multiple Choice

If your teacher asked you to make categorical observations about the class’s pet hamster, which group of words might be used?

• A mass of 3 kg, 11 cm long, age of 16 months

• A mass of 3 kg, 11 cm long, cute

• A long hair, white and brown colored, soft

• A temperature, length, weight

Multiple Choice

Which of the following is an example of quantitative data?

• High School Graduate or Not

• Monthly paycheck amount

• Whether or not you are employed

• What type of vehicle you drive

Multiple Choice

Which of the following is an example of quantitative data? 

• The color of your car

• A person's state of residence

• A person's Zip Code

• A Person's Height

Multiple Choice

How many states have you visited in your lifetime?

• Categorical

• Quantitative

The World Bank recognizes 213 countries.
Data has been collected on each in the
dataset AllCountries

Use the dataset to answer the questions below:

What are the cases?

What are the variables?

Are the variables Categorical or Quantitative?

Which variable is the explanatory variable, and which are response
variables?

Multiple Choice

A sociologist is studying the relationship between early childhood nutrition and academic achievement in middle school among children in a certain city. Which of the following statements about the variable “early childhood nutrition” is correct?

• Early childhood nutrition is a response variable.

• Early childhood nutrition is an explanatory variable.

• Since there is not a clear explanatory-response relationship in this scenario, we cannot classify early childhood nutrition as either explanatory or response.

Multiple Choice

We wish to investigate the relationship between the number seeds planted in a garden and the number of fruit grown. The explanatory variable (EV) is

• The number of fruit grown

• The amount of soil in the garden

• The number of hours spent watering the plants

• The number of seeds planted

Multiple Choice

Which of the following is true?

• We use the response variable to explain changes that might be observed in the explanatory variable.

• The explanatory variable is the variable we expect to be explained by the response variable

• The response variable is also known as the predictor variable

• The explanatory variable is used to explain or predict the value of the response variable

Multiple Choice

Studies have shown that the marks received by a student depend on the amount of hours spent studying. Which is the response variable (RV)?

• Hours spent studying

• Marks

• Both Marks and Hours spent studying

• None of the above

In the AllCountries dataset, use the questions below to determine which variables are explanatory, and which are response:

How do we collect data from large populations?

Example:

Can we trust all samples to best represent the whole population?

So what happened?

The newspaper got their information from a sample of voters, why couldn’t
they correctly connect the results of their sample to that of the population overall?

We need to look out for sampling bias

So how do we select a RANDOM sample?

STRATEFIED
SAMPLING

SYSTEMATIC
SAMPLING

CLUSTER
SAMPLING

Which is Which??

Which method of Sampling is used?

What if you could choose? What method would
be most effective?

Suppose we are interested in estimating the malaria rate in a densely
tropical portion of rural Indonesia. We learn that there are 30 villages in that
part of the Indonesian jungle, each more or less similar to the next. Our goal
is to test 150 individuals for malaria. What sampling method should be
employed?

Drag and Drop

Interview every 10th student who enters the school in the morning.

Placeholder

Drag these tiles and drop them in the correct blank above

systematic

simple random

voluntary response

convenience

Drag and Drop

Assign each car in a dealership a number and then use a random-number table to select the cars to be inspected.

Placeholder

Drag these tiles and drop them in the correct blank above

simple random sample

systematic

convenience

Self - selected (volunteer)

Drag and Drop

Marianne wanted to know students' opinion on the new schedule at school. She survey's the first 30 students who come into her class.

Placeholder

Drag these tiles and drop them in the correct blank above

Convenience Sampling

Systematic Random Sampling

Simple Random Sampling

Volunteer response

Drag and Drop

A teacher wants to know how well her students are doing on a topic. She randomly picks one class to survey.

Placeholder

Drag these tiles and drop them in the correct blank above

Cluster

Simple Random

Stratified

Systematic

Drag and Drop

A teacher splits her classes up by period. She then randomly picks 3 students from each period to do a survey.

Placeholder

Drag these tiles and drop them in the correct blank above

Stratified

Simple Random

Cluster

Systematic

Drag and Drop

A is a small portion of the population used to gather data from.

Placeholder

Drag these tiles and drop them in the correct blank above

Sample

Systematic Sampling Method

Population

Bias

Dropdown

A is a large group that includes everything being studied.

Select answer

Many times in studying a sample, we need to identify how different variables affect each other.

Association vs Causation

For each example below, identify how the variables
are affected by each other: Association, Causation, or
Unknown

Is there a link between the number of vehicle registrations and life expectancy?

Are they associated or causal? Or is there something else that links
them?

Multiple Choice

Sam's mom claims the number of hours spent playing video games bring down his grades so he should stop playing video games. Is this association or causation?

• Association

• Causation

• Neither

Multiple Choice

A survey showed that sleeping with a night light was positively associated with nearsightedness. Is this association or causation?

• Association

• Causation

• Neither

Multiple Choice

A study showed a positive relationship between students owning a cell phone and driving a car to school. Is this association or causation?

• Association

• Causation

• Neither

Multiple Choice

A study showed a positive relationship to the sound level of listening to music and hearing loss. Is this association or causation?

• Association

• Causation

• Neither

Multiple Choice

Ashley was researching tuition costs for college and noticed the cost has increased over the last ten years. As she was researching, she noticed that there has also been an increase in the number of electric cars sold. Is this association or causation?

• Association

• Causation

• Neither

Multiple Choice

The number of firemen increases as the size of the fire increases. Is this association or causation?

• Association

• Causation

• Neither

Exercises:

Migraine and acupuncture. A migraine is a particularly painful type of headache,
which patients sometimes wish to treat with acupuncture. To determine whether
acupuncture relieves migraine pain, researchers conducted a randomized
controlled study where 89 females diagnosed with migraine headaches were
randomly assigned to one of two groups: treatment or control. 43 patients in the
treatment group received acupuncture that is specifically designed to treat
migraines. 46 patients in the control group received placebo acupuncture (needle insertion at nonacupoint locations). 24 hours after patients received acupuncture, they were asked if they were pain free. Results are summarized in the contingency table below:

At first glance, does acupuncture appear to be an effective treatment for
migraines? Explain your reasoning.

Exercises:

Exercises:

During the study air pollution levels were measured by air quality monitoring
stations. Length of gestation data were collected on 143,196 births between the
years 1989 and 1993, and air pollution exposure during gestation was calculated for each birth.

(a)

Identify the population of interest and the sample in this study.

(b)

Comment on whether or not the results of the study can be generalized to the population, and if the findings of the study can be used to establish causal relationships.

Exercises:

A survey was conducted on 193 Duke University undergraduates who took an
introductory statistics course in 2012. Among many other questions, this survey
asked them about their GPA, which can range between 0 and 4 points, and the
number of hours they spent studying per week. The scatterplot below displays the relationship between these two variables.

(a)

What is the explanatory variable and what is the response variable?

(b)

Describe the relationship between the two variables. Make sure to discuss unusual observations, if any.

(c)

Is this an experiment or an observational
study?

Exercises:

A study published in the Journal of Personality and Social Psychology asked a group of 200 randomly sampled men and women to evaluate how they felt about various subjects, such as camping, health care, architecture, taxidermy, crossword puzzles, and Japan in order to measure their dispositional attitude towards mostly
independent stimuli. Then, they presented the participants with information about a
new product: a microwave oven. This microwave oven does not exist, but the
participants didn’t know this, and were given three positive and three negative fake
reviews. People who reacted positively to the subjects on the dispositional attitude
measurement also tended to react positively to the microwave oven, and those who reacted negatively also tended to react negatively to it. Researchers concluded that “some people tend to like things, whereas others tend to dislike things, and a more thorough understanding of this tendency will lead to a more thorough understanding of the psychology of attitudes.”

(a) What are the cases?
(b) What is (are) the response variable(s) in this study?
(c) What is (are) the explanatory variable(s) in this study?
(d) Does the study employ random sampling?
(e) Is this an observational study or an experiment? Explain your reasoning.
(f) Can we establish a causal link between the explanatory and response variables?
(g) Can the results of the study be generalized to the population at large?