Statistical Tests
Is this variable continuous or categorical: “Mood score from 0–100”?
Continuous
The variable a researcher manipulates is called what?
IV
Changing your hypothesis after seeing your results is called what?
HARK-ing
“Increasing background noise reduces reading comprehension.” What is the IV?
Noise Level
Studying only engineering majors and trying to generalize to all college students threatens what?
External Validity
I want to examine whether the number of hours students sleep on a typical weeknight predicts their daily concentration score (rated 0–10)?
What statistical test should I use?
Pearson's r correlation coefficient
What must be included for a study to count as an experiment?
Random assignment!!!!!!!!!
Editing data or changing statistical analysis strategy only to get a significant result is an example of what?
p-hacking
A researcher tests whether exercise intensity predicts mood. What is the DV?
mood
Collecting data on sleepiness only in the morning for one group and only in the evening for another threatens what?
Internal Validity
I want to test whether attending office hours (yes/no) is related to whether a student passes or fails an exam (pass/fail).
Chi-square test of independence
What are the three requirements for a causality claim?
1. covariance/ association
2. temporal precedence
3. high internal validity/ can limit the third-variable problem
A researcher approaches students during class to participate in a survey, and many feel they cannot say no. What ethical issue is present?
Coercion/ pressure to participate
Imagine a bar graph with the X axis indicating "types of sports" and the Y axis indicating "number of students". Which is the DV?
Number of students
A team compares two study methods, but one group meets online and the other meets in person. What validity issue is this?
Mode-of-delivery confound threatening internal validity
A p-value of .27 means you should do this with the null hypothesis.
fail to reject the null hypothesis
A researcher wants to understand whether the presence of plants in indoor spaces is associated with people’s alertness. They visit several campus buildings and rate each person’s alertness using a short behavioral checklist. Before rating, the researcher notes whether the person is in an area that happens to have indoor plants or in an area without plants.
To keep observations consistent, the researcher goes at the same times of day, rotates through predetermined locations, and uses the same checklist for every participant. They do not tell people where to sit and do not alter the environment.
Q: Is this an experiment or a naturalistic observational design? and WHY?
Naturalistic observation — even though the researcher uses structured procedures (set times, set locations, standardized checklist), they are not manipulating the environment or assigning people to plant vs. no-plant areas. Participants naturally end up in each setting, so there is no random assignment.
A recycling study records time of day, location, and the participant’s face. What ethical principle is being violated?
Protection of confidentiality / collecting unnecessary identifying information
A study compares these types of music: rap, country, classical. How many levels does the IV have?
3
A study testing relaxation techniques includes participants tested right before midterms and others tested during a low-stress week. What validity problem does this cause?
Time-based confound threatening internal validity (stress levels differ for reasons unrelated to the study)
Your correlation has p = .04, but the CI is very wide. What additional information does the CI give you about the result?
It tells you how large or small the true "effect" might be in the population (the possible range of the effect). Using this range, we can interpret:
1. If the relationship between the variables we are interested in is meaningless (if interval is close to 0) or very meaningful (if interval is close to -1 or 1).
2. If our estimate in our sample was precise or not, depending on how wide the confidence interval is.
A researcher wants to understand how often people check their phones while waiting in public spaces. They visit bus stops around the city at different times of day and quietly observe each person for two minutes, recording:
whether the person is alone or around others, and
how many times they look at their phone.
The researcher does not change anything about the setting and does not interact with the people being observed.
Q: This is a naturalistic observation. What could I do to turn this into a true experiment?
Introduce manipulation + random assignment — for example, randomly assign people to wait in a “social condition” (someone else is placed nearby) or an “alone condition” and measure their phone-checking behavior.
During a study on food choices in a cafeteria, the researcher stands near the salad bar and occasionally smiles or nods when someone picks a healthy option. These subtle cues could push people toward certain choices.
What is the researcher doing that could be considered an ethical concern?
The researcher is unintentionally impacting the outcome through nonverbal cues. The researcher should not impact participant behavior.
A study examines whether instructor enthusiasm (high vs. low) influences both test performance and class attendance. Identify all variables.
IV: Instructor enthusiasm
DV1: Test performance (continuous)
DV2: Class attendance (categorical or count-based depending on measurement)
Researchers want to test whether listening to music improves productivity. They compare students working in a “music room” to students working in a “quiet room.”
However, the music room happens to have big windows with natural light, while the quiet room is in the basement and has no windows. The music room is also warmer because it’s next to the building’s boiler room.
Identify two confounds or threats to internal validity in this study.
Lighting differences:
Natural light vs. fluorescent light could influence alertness/eye strain.
Time-of-day differences:
Different rooms may be used by different types of students at different times.
Activity differences:
Students in one room might be doing harder/easier work, influencing focus scores independently of room environment.
Noise differences:
One room is busy/noisy, the other is quiet — noise itself affects focus.