Standard scores and raw scores and percentiles…oh my!
by Jessica Klein, MS, CCC-SLP
Nervous. Anxious. Excited. Parents may feel a variety of emotions when their child is being evaluated. When they receive a copy of the evaluation report, they are eager to see the results. They want to quickly determine how well their child did. Unfortunately, deciphering this information on their own doesn’t always happen. Parents are often left confused by pages filled with numbers and unfamiliar terms. A face-to-face meeting to explain these results is essential. It is also essential that we fully understand these results before explaining them to parents.
Listed below are some commonly asked questions and answers regarding evaluations.
What is the difference between a raw score and a standard score?
A raw score is based on the number of items that were answered correctly on a test or a subtest. For example, if a subtest has 20 items and the child answered 14 of them correctly, the raw score is 14. This raw score is then converted to a standard score. Standard scores between 85-115 fall within the average range. Standard scores can be used to track growth over time.
What does it mean when a standard score stays the same year-to-year?
Standard scores that stay the same year-to-year indicate that a student is making consistent progress. They are making a year’s worth of growth in a year’s worth of time. Standard scores that increase significantly in a year indicate that a student has made more than a year’s worth of progress. Standard scores that significantly decrease may indicate that a student has made progress but not at the same rate as his peers.
What is a confidence interval?
A confidence interval is a range of scores in which the child’s “true score” likely falls. Confidence intervals are reported using percentages, typically 90% or 95%. For example, a 90% confidence interval provides the range of scores that with 90% certainty contains the child’s “true score.” The student may have had an off day on the date of the assessment. The examiner could have made an error. The confidence interval accounts for these possibilities.
What does the percentile rank signify? Does it indicate the percentage of questions answered correctly?
The percentile rank is not the percentage of questions that the child answered correctly. The percentile rank tells how many same-age students scored lower than the child. For example, if a child is in the 75th percentile, 75% of students the same-age tested below that child’s score.
Evaluations provide valuable information. Professionals who fully understand what the scores indicate are better equipped to explain the information to parents. Their shared knowledge results in a team that understands and is ready to address the child’s needs.