The trial urban district assessment (tuda) is a government-sponsored study of student achievement in large urban school districts. tuda gives a mathematics test scored from 0 to 500. a score of 262 is a "basic" mathematics level and a score of 299 is "proficient." scores for a random sample of 1 100 eighth-gr ders in dallas had 271 with standard error 1.3.

(a) we don't have the 1100 individual scores, but use of the t procedures is surely safe. why? o
a. because the sample size is very large.
b. because the sample doesn't have outliers.
c. because the data haya strong skew.
d. because use of the t procedures is always safe.

A. Because the sample size is very large.

Step-by-step explanation:

The sample is quite large, so the t test is safe. With a sample size of at least 100, this test is going to be safe.

So the correct answer is:

A. Because the sample size is very large.

starting with:    

5 + x - 12 = 2x - 7   

5 + x - 12 - x = 2x - 7 - x (subtract x from both sides)   

5 - 12 = x - 7 (combine and cancel x's from both sides)   

5 - 12 + 7 = x - 7 + 7 (add 7 to both sides)   

0 = x (add numbers together on both sides)       

so in order for the equation to be true, x must be 0.   

trying x = -0.5   

5 + x - 12 = 2x - 7 (original equation)   

5 + -0.5 - 12 = 2(-0.5) - 7 (plug in value of x)   

5 + -0.5 - 12 = -1 - 7 (did multiplication)   

-7.5 = -8 (did addition on both sides)       

since -7.5 is obviously not equal to -8, the value of -0.5 for x is wrong.   

trying x = 0   

5 + x - 12 = 2x - 7 (original equation)   

5 + 0 - 12 = 2(0) - 7 (plug in value of x)   

5 + 0 - 12 = 0 - 7 (did multiplication)   

-7 = -7 (did addition on both sides)       

since -7 equals -7, that demonstrates that the value of 0 for x is correct.   

trying x = 1   

5 + x - 12 = 2x - 7 (original equation)   

5 + 1 - 12 = 2(1) - 7 (plug in value of x)   

5 + 1 - 12 = 2 - 7 (did multiplication)   

-6 = -5 (did addition on both sides)       

since -6 is obviously not equal to -5, the value of 1 for x is wrong.