A brief description of the Purdue Pegboard Test may be found at Shirley Ryan AbilityLab.
A Quick Start Guide and the User Manual may be found at Lafayette Instrument.
A z-score describes a client’s raw score (X) on an assessment in relation to the population mean (μ) in terms of standard deviation units (σ). In other words, it answers the question: “How many standard deviations above or below the mean is a client’s score?” A negative z-score indicates that the client’s raw score falls below the mean; a positive z-score indicates that the client’s raw score falls above the mean. Z-scores are often used to qualify clients for therapy services. Especially in pediatric occupational therapy, clients who score more than one and a half standard deviations below the mean (z-score = -1.50) qualify for services. Often in adult services, clients who score more than two standard deviations below the mean (z-score = -2.00) qualify for services. Z-scores are always calculated to two decimal points. The equation for calculating a z-score is as follows:
z-score = (X-μ)/σ
To interpret the z-score, it is important to consider the units of measurement (such as pounds of force or time in seconds). In cases where a higher score indicates better performance (e.g., pounds of force), if a client’s score is higher than the mean, the z-score will always be positive. In cases where a higher score indicates poorer performance (e.g., time in seconds), if a client’s score is higher than the mean, the z-score will always be negative.
To calculate the client’s z-score, follow the following link.