In statistics, a standard score is a dimensionless quantity derived by subtracting the population mean from an individual raw score and then dividing the difference by the population standard deviation. This conversion process is called standardizing or normalizing; however, "normalizing" can refer to many types of ratios.

Standard scores are also called z-values, z-scores, normal scores, and standardized variables; the use of "Z" is because the normal distribution is also known as the "Z distribution". They are most frequently used to compare a sample to a standard normal deviate (standard normal distribution, with μ=0 and σ=1), though they can be defined without assumptions of normality.

The standard score indicates how many standard deviations an observation is above or below the mean: the standard deviation is the unit of measurement of the z-score. It allows comparison of observations from different normal distributions, which is done frequently in research.

What is the critical z-value
What is the critical z-value that corresponds to a confidence level of 86%

I hope it will teach me the fundamentals for 11th grade and 12th grade Math.
I teach math to 9th grade -12th grade at a small city school in North Carolina. Knowing that each student in NC has to score levels 3 or 4 on the EOC Algebra 1 test to graduate, any real-life application type problems would be beneficial to the success of my students. Knowing also that matrces are heavily tested on the NC EOC test, this website appears that it would be helpful. Our textbooks do not offer many examples of matrices . Thank you.