Defining Outliers using z Scores
While outliers are generally understood as extreme values within a dataset, scores provide a formal, quantitative method for identifying them. Commonly, outliers are defined as scores that fall more than three standard deviations away from the mean. In standardized terms, any score with a score strictly less than or strictly greater than is classified as an outlier.
0
1
Tags
KPU
Research Methods in Psychology - 4th American Edition @ KPU
Related
Statistical z Score Formula
Defining Outliers using z Scores
Usefulness of z Scores
Formula for the z Score
Importance of z Scores
In statistical analysis for psychological research, what does a z score indicate about a particular raw score?
In a psychological study, researchers calculated z scores for participants' performance on a memory task. Arrange the following participants in order from the highest score to the lowest score based on their relative position in the distribution.
A psychologist is analyzing how various statistical adjustments to a research dataset affect the resulting standardized scores. Match each statistical change with its specific impact on the participants' scores.
A researcher is comparing a student's performance on two different psychological assessments that use different measurement scales. The researcher concludes that because the student achieved a score of on the first assessment and a score of on the second, the student's relative standing is higher on the first assessment. This conclusion is statistically valid.
In psychological research, what is the primary function of converting a raw score into a score?
Match each score with the statement that accurately describes its relative location in a distribution of psychology test scores.
In a psychological study on social anxiety, the sample mean is 50 and the standard deviation is 10. A participant who receives a raw score of 35 on this assessment has a z-score of _____.
Excluding Outliers
Handling Valid Extreme Outliers
Example of an Outlier
Sensitivity of the Mean to Outliers
Defining Outliers using z Scores
Reaction Time Outlier Example
Impact of Outliers on the Range
Identifying Outliers Using z Scores
Handling Outliers
What term is used to describe an extreme score that falls significantly above or below the rest of the scores within a distribution?
In psychological research, an outlier in a dataset always indicates that an error occurred during data collection, such as an equipment malfunction or participant misunderstanding.
In psychological research, outliers can arise from various sources. Match each research scenario with the most likely reason for the extreme score described.
A researcher identifies a score in a dataset that falls significantly below the rest of the distribution. Arrange the following steps in the logical analytical sequence used to investigate and address this extreme value.
You are constructing a research protocol for a study on the cognitive effects of extreme stress. To ensure that your final dataset can systematically distinguish between genuine cases of 'stress resilience' (valid outliers) and 'task confusion' (measurement errors), which design element should you integrate into your data-collection phase?
Sexual Partners Survey Outlier Example
Outlier in Beck Depression Inventory Scores
A researcher is evaluating a dataset where a single participant's score is , while all other scores are between and . After confirming the participant understood the task perfectly and no errors occurred, the researcher decides to retain the score. This decision reflects a judgment that the extreme value is a(n) _____ which, despite its potential to skew the mean, represents a genuine and valid case within the study.
A researcher measures anxiety in 50 participants and finds that 49 scores fall between 20 and 45, but one participant scores 95. This extreme value, which may reflect a genuinely anxious individual or a data collection error, is called a(n) _____.
A researcher administering a depression inventory notices one participant scored far higher than the rest of the sample. If the researcher confirms this participant is indeed clinically depressed and no data entry or equipment errors occurred, this extreme score is no longer considered an outlier.
Match each description of a research scenario that produces an extreme score with its corresponding source of outlier.
When conducting data cleaning on a newly collected psychological dataset, order the stages a researcher should follow to systematically identify and categorize an extreme score.
Learn After
When using scores to formally identify extreme values in a dataset, which of the following provides the commonly accepted quantitative definition of an outlier?
If a researcher calculates standardized scores for a dataset and finds that a participant has a score of , this score should be formally classified as an outlier according to the common quantitative criterion.
A researcher is screening data from a study on reaction times. According to the standard quantitative criterion for outliers (scores falling more than 3 standard deviations from the mean), match each participant's calculated score to its correct classification.
A researcher is evaluating a dataset of test scores to prioritize which cases should be investigated for potential measurement error. Based on the formal definition of an outlier (scores with a score beyond ), rank these four participants from the highest priority for investigation (the most extreme outlier) to the lowest priority (the most typical score).
Based on the formal quantitative method for identifying outliers, which of the following conditions must a score meet to be classified as an outlier?
According to the formal quantitative definition of an outlier, only scores that fall strictly more than three standard deviations above the mean (i.e., ) are classified as outliers.
When researchers define outliers as scores with a score strictly greater than +3.00 or strictly less than -3.00, they are identifying data points that fall more than 3 _____ away from the mean.
A researcher computes scores for participants in a cognitive task study. Apply the formal outlier criterion (strictly or strictly ) to match each participant's score to the correct classification.
A researcher computes scores for five data points and obtains the following values: , , , , and . Carefully analyzing which values satisfy the formal outlier criterion (strictly or strictly ), the total number of outliers in this set is _____.
A researcher wants to ensure her outlier-handling procedure is transparent and defensible under peer review. Evaluate the following actions and arrange them in the order that best reflects sound, justifiable research practice when using scores to define and handle outliers.
Describe the formal, quantitative method for identifying outliers in a dataset using scores. In your description, specify the exact thresholds used to classify a score as an outlier, and explain what these thresholds represent in terms of the dataset's standard deviation and mean.
Based on the quantitative threshold for outliers using scores, explain whether the researcher should formally classify this student's sleep duration as an outlier. Justify your decision by explaining what a score of means conceptually in relation to the sample mean and standard deviation.
A clinical psychology researcher calculates scores for anxiety symptom severity in a sample of participants. They obtain the following scores for three participants: Participant A (), Participant B (), and Participant C (). Apply the formal quantitative outlier criterion to determine which of these participants, if any, have scores that are classified as outliers, and explain why.