Salary Report Documentation

Information Technology Job

MySQL
Database Professional

United States Location

United States of America
Nationwide
Metropolitan Areas

Competitive Position® Salary Report

Source Documentation

Web Site Want Ads

The Salary Report is based on a sample of Want Ads listed in the career web sites:

  • CareerBuilder.com
  • ComputerJobs.com
  • Dice.com
  • Craigslist
  • Monster.com
  • USA Jobs.

Duplicate Want ads found in the same month were eliminated.

Please Note: The career web sites only act as venues for job postings and are not responsible for the content of the want ads. They are not associated with and do not endorse this Salary Report.

MySQL - Database Professional

USA

Collected Past 3 Years

The sample was collected in the 157 weeks between:

  • Tuesday April 1, 2008
  • Friday March 25, 2011.
Large Number of Want Ads

844 Want Ads were collected.

Each want ad listed:

  • Salary
  • Required Experience
  • Qualifications for a MySQL - Database Professional
  • Location in a US City.

Statistical Documentation

MySQL - Database Professional

Regression Analysis

The regression equation of the average salary is derived.

The regression equation minimizes the variance of the salaries across the sample of want ads.

The Regression Equation

Salary for MySQL - Database Professional is lowest at entry level, increases rapidly with the first years of experience and approaches a ceiling as experience matures.

When Perl is required Salary is Higher.

When ETL is required Salary is Lower.

When San Francisco-Oakland-San Jose, CA is required Salary is Higher.

$50,661 Entry Level Salary average
+ $5,826 with Perl required
- $3,878 with ETL required
+ $21,777 with San Francisco-Oakland-San Jose, CA required
+ ( $18,016 ∗ ln(Number of Years of Experience) )
= Salary Average.

Note: Since the natural logarithm, 'ln', is not defined at zero, +1 is always added to the number of years of required experience.

Collinearity Tested

The variables of the regression equation are determined to be independent by a 95% one-tailed t-distribution test.

Residuals

Many want ads state a salary that is either greater or less than the Salary Average.

A residual is equal to the difference between the salary offered in a want ad and the salary as calculated by the regression equation for the want ad.

The variance is the sum of the squared residuals for the entire sample of want ads.

R Squared Statistic

The R Squared statistic is a measure of the 'goodness of fit' of the regression equation.

It states the percent of the sum of the squared salaries in the sample of want ads calculated by the regression equation:

  • 19.89% = R Squared.

The remaining percentage is explained by the variance:

  • 80.11% = Sum of Squared Residuals.

An R Squared statistic of 100% would indicate that all want ads offered the average salary. A reasonable degree of variability should be expected due to the many factors influencing individual want ads.

t-Distribution Statistical Tests

The t-Distribution is applied to test if a variable within the salary regression equation is equal to zero.

A variable can be insignificant if its standard deviation is too large.

The t-Distribution multilpied by a variable's standard deviation determines the 95% Confidence Interval and the probability the variable is equal to zero salary.

Significant confidence is placed in a regression equation variable when the low point of the 95% Confidence Interval is above zero. Even more confidence is placed when there is little probability that the variable is equal to zero salary.

1.9628 is the factor of the t-Distribution where only 2.5% of the sample of 844 want ads have higher values.

The Salary Average, Standard Deviation, 95% Probability Range and Probability of zero salary for each variable:

Entry Level Salary Average = $50,661
Standard Deviation = $3,986
  • 95% Probability Range = $42,837 to $58,486
  • there is less than a one-hundredth of one percent ( < 00.01 % ) probability that the Entry Level salary is equal to zero
Perl = + $5,826
Standard Deviation = $1,885
  • 95% Probability Range = $2,126 to $9,526
  • there is a 2.1 tenth of a percent ( 00.21 % ) probability that the Perl qualification determines zero salary
ETL = - $3,878
Standard Deviation = $1,788
  • 95% Probability Range = - $7,387 to - $369
  • there is a 3.04 percent probability that the ETL qualification determines zero salary
San Francisco-Oakland-San Jose, CA = + $21,777
Standard Deviation = $1,673
  • 95% Probability Range = $18,494 to $25,061
  • there is less than a one-hundredth of one percent ( < 00.01 % ) probability that the San Francisco-Oakland-San Jose, CA qualification determines zero salary
Experience = $18,016 ∗ ln(Number of Years of Experience + 1)
Standard Deviation = $2,326
  • 95% Probability Range = $13,452 to $22,581
  • there is less than a one-hundredth of one percent ( < 00.01 % ) probability that Experience determines zero salary.
F-Distribution Statistical Test

The F-Distribution probability considers whether the Salary Average regression equation is statistically equivalent to an equation set to zero.

The regression equation can be insignificant if its standard deviation is too large.>

The lower the F-Distribution probability the more confidence is given to the regression equation:

  • The MySQL - Database Professional Salary Average equation has less than a one-hundredth of one percent ( < 00.01 % ) probability that it is equal to zero.
Heteroscedasticity Correction

The Salary Average regression equation required a correction for Heteroscedasticity.

The residuals are not uniform for all job characteristics:

  • the residuals are larger when Graduate Degree is required
  • the residuals are larger when Perl is required
  • the residuals are smaller when ETL is required

This additional information was factored into the analysis by dividing each want ad by its level of variance found in the heteroscedasticity regression equation:

  • (e^(4.2698 + 1.2908GraduateDegree + 0.8864PerlScript + -0.6244ETL))^.5.

The heteroscedasticity regression equation is verified to have an F-Distribution probability of less than 1 tenth of 1 percent chance ( < 00.10 % ) of not existing.

Each job characteristic of the heteroscedasticity regression equation is verified to have a t-Distribution probability of less than a 1 percent chance of not existing.

Standard Deviation

The Standard Deviation is the average residual found in a want ad.

$21,269 = Standard Deviation.

Salary Range

The Salary Ranges are calculated by adding ±(Standard Deviation ∗ t-Distribution Statistic) to the Salary Average.

The Salary Range factors are:

$21,269 = Standard Deviation
t-Distribution Statistics for the 844 want ads of the sample =
0.1257 for 10% Salary Range
0.3187 for 25% Salary Range
0.4309 for 33% Salary Range
0.6748 for 50% Salary Range
0.968 for 67% Salary Range
1.2826 for 80% Salary Range
1.6467 for 90% Salary Range
1.9628 for 95% Salary Range
Experience

The 95% range of Experience is calculated by adding ±(Standard Deviation ∗ t-Distribution Statistic) to the Experience Average:

  • 1 Year and 8 Months = Standard Deviation of Experience
  • 1.9628 = t-Distribution statistic for 95% Experience Range.
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