Algebra students in a local high school use a computer-based program to brush up on algebra skills to be assessed by a test. The program claims that 80% of students using the program will pass the test. After an early pilot of the new program, only 35 of 50 students passed the test.A 1-proportion z test is going to be conducted to see if there's evidence that the true passing rate is less than what was claimed. The null hypothesis is

p = 0.80.

What is the value of z, the test statistic? (Round your answer to two decimal places.)