document.write( "Question 1188837: The standard deviation of the pollution by-products released in the burning of 1 gallon of gas is 2.3 ounces. A random sample of 20 automobiles tested produced a standard deviation of 1.9 ounces. Is the standard deviation really less than previously thought? Use α = 0.05. \n" ); document.write( "
Algebra.Com's Answer #820273 by Theo(13342)\"\" \"About 
You can put this solution on YOUR website!
i'm not sure if this is right, but here goes.
\n" ); document.write( "the standard deviation for the population is assumed to be 2.3 ounces.
\n" ); document.write( "with a sample size of 20, the standarfd error is 2.3 / sqrt(20) = .514296 rounded to 6 decimal places.
\n" ); document.write( "z-score = (x - m) / s
\n" ); document.write( "x is the mean of the sample.
\n" ); document.write( "m is the mean of the population.
\n" ); document.write( "s is the standard error.
\n" ); document.write( "formula becomes:
\n" ); document.write( "z = (1.9 - 2.3) / .514296 = -.77776 rounded to 5 decimal places.
\n" ); document.write( "critical z-score at one-tailed signjificance level of .05 is equal to -1.645.
\n" ); document.write( "since the test z-score is less than that, there is not sufficient information to say that the population standard deviation is less than 2.3.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "
\n" );