## Question 155:

1## Answer:

No answer provided yet.The proportion parameter p, is usally estimated using the sample proportion p-hat (that's a p with a little hat on it). The proportion is found by taking the mean of a sample from a binary/discrete variable (such as the proportion of users completing a task, the pass-fail grade on a test).

X-bar is usually used to represent the sample mean of a continuous variable, such as time-on-task, blood-pressure, weight, height. So p and x-bar both estimate the mean, just of different types of data (continuous or discrete). *s* is the sample estimate of the population standard deviation, which is usually represented as a lower-case sigma.