Skewness – Floor & Ceiling Effects

In this video I explain how skewness in a sample may be caused by a floor or a ceiling effect, in which the measurement isn’t able to capture variability at the low or high end of a population’s distribution. A floor effect will result in a positively skewed sample, while a ceiling effect will result in a negatively skewed sample, … Read More

Skewness – Positive & Negative Skew

In this video I explain one way in which a distribution can deviate from normality, which is skewness. I explain the difference between positive and negative skew, and how these can be seen in histograms, stem and leaf displays, and box and whisker plots. I then discuss the effect of skew on measures of central tendency and consider possible reasons … Read More

Reliability of Assessments

In this video I explain the difference between validity and reliability and then describe several ways of assessing reliability including split-half reliability, test-retest reliability, equivalent-form reliability, and the related concept of standardization. Don’t forget to subscribe to the channel to see future videos! Have questions or topics you’d like to see covered in a future video? Let me know by … Read More

Assessing Assessments – Types of Validity

In this video I explain how we assess the validity of assessments that have been created for a particular property (such as intelligence). There are several types of validity that can be assessed including construct validity, face validity, content validity, and criterion-related validity (concurrent and predictive). I briefly describe each of these types of validity and how they tell us … Read More

Research Methods Practice Questions

The following video includes 10 practice multiple choice questions related to research methods and statistics in psychology. I hope that these can help you to test and assess your own knowledge and provide practice retrieving the terms, ideas, and concepts that you’ve learned. You can also find a PDF with the practice questions and an answer key below the video. … Read More

Research Methods & Statistics Knowledge Organizer

Here’s a knowledge organizer I’ve created of the most essential concepts for research methods and statistics in an introductory psychology course. These knowledge organizers are designed to help you identify the most important factual knowledge you need to have in order to engage in the more challenging activities of discussing, writing about, and applying the concepts. If you find these … Read More

Ethical Guidelines for Psychological Research

In this video I explain the major ethical guidelines for conducting research in psychology with human subjects including informed consent, freedom from coercion, protection from harm, risk-benefit analysis, anonymity and/or confidentiality, and debriefing. Don’t forget to subscribe to the channel to see future videos! Have questions or topics you’d like to see covered in a future video? Let me know … Read More

External Validity

In this video I explain external validity (or ecological validity) and criticisms of artificiality that can arise from laboratory experimentation. I also explain naturalistic observation and field experiments as ways of overcoming artificiality and collecting real-life data, though both of these approaches have the disadvantage of sacrificing control over potential confounding variables. Don’t forget to subscribe to the channel to … Read More

Internal Validity

In this video I explain the concept of internal validity and how it acts as a checklist for considering whether an independent variable has been effectively manipulated, a dependent variable has been measured without bias, and a clear pattern can be found in the data. I also mention the importance of avoiding simple yes/no answers and remembering that all of … Read More

Frequency Distributions, Normal Curves, and Skew

In this video I explain how a frequency distribution can create a visual representation of our data. I also describe a normal curve or “bell curve” and what it means for mean, median, and mode. Then I consider skewed distributions with positive or negative skew. Don’t forget to subscribe to the channel to see future videos! Have questions or topics … Read More