A Cognitive Psychologist Has Developed a Computer Simulation of Memory

Multiple Choice

A cognitive psychologist has developed a computer simulation of memory processes that generates a simulation of reaction times in response to the presentation of previously learned stimuli.The program has been designed to produce a mean reaction time of 200 msec with a standard deviation of 20.The psychologist is worried that the program has stopped working properly because the last 16 trials have produced a mean reaction time of 190 (with the expected standard deviation of 20) .Which of the following statements is true?

A) A z-score could be calculated for these data.
B) A z-score could be calculated for these data but no inferences could be made.
C) A z-score could be calculated for these data but no inferences could be made because it is impossible to get ethical clearance for computer simulations.
D) A z-score could be calculated but it could not be used to make inferences because the population standard deviation is unknown.
E) A z-score could be calculated but it could not be used to make inferences because the population standard deviation is likely to be a negative number.