The Preliminary SAT, or PSAT, is four hours of fingernail-biting tension for just over 1.5 million high school juniors every year. The exam isn't essential for students' college applications, but PSAT scores can help students earn other honors and predict their future success.

What the PSAT Measures

The PSAT is a standardized, multiple-choice examination covering three distinct subject areas: critical reading, mathematics and writing skills. Questions in the critical reading section require students to answer questions about the main idea, structural approach or author's intent of short passages. The mathematics section includes questions on a variety of subjects within mathematics including algebra, probability and statistics, and geometry. Calculus is not included on the PSAT. The writing skills section asks students to improve problematic writing by changing the grammar, vocabulary and tone of a sentence. Some questions ask students to improve a paragraph, for example, by inserting an appropriate topic sentence.

How PSAT Scores Work

A student's total PSAT score is the composite value of a student's score on each of the three sections. The minimum score on each section is 20 and the maximum 80, so the minimum composite score is 60 and the maximum is 240. Each of these scores is a "scaled score," meaning they reflect how well a test-taker did relative to others rather than how many questions she got right. For example, a score of 68 on the math section would place a student in the 94th percentile of test-takers in the math section. Among high school juniors, the median composite score fall around 141.

Correlation with SAT Scores

The SAT follows the same basic scoring model as the PSAT, but with an extra zero tacked onto the end of a PSAT score to make it an SAT score. For example, a PSAT score of 211 translates to an SAT score of 2110. Since the scoring technique is similar and both tests cover the same basic areas, PSAT scores are a reliable indicator of SAT scores. The relationship isn't perfect, however. A PSAT score doesn't exactly match up with an equivalent SAT score. Instead, the PSAT predicts a student's SAT score will fall in a given range. For example, a student who makes a 49 on the PSAT's math section would be expected to score anywhere from 460 to 560 on the SAT math section, according to Montgomery Educational Consulting.

PSAT and National Merit Scholarships

The PSAT is also the primary criteria for receiving a National Merit Scholarship. The National Merit Scholarship corporation selects approximately 50,000 high scorers from among the 1.5 million high school students who take the test each year. Two-thirds of these are named "commended scholars," while 16,000 are selected as semi-finalists for the scholarship. About 15,000 of the semi-finalists become finalists, and about 9,000 of them will receive some form of National Merit Scholarship award. PSAT scores are the only criterion for advancing to the semi-final round, though finalists and winners are selected according to their grades, too.