Select all the correct answers. Select all the studies in which the results may have been skewed by bias. For each study, assume a normal distribution.

a study of employee satisfaction, with 25% of the data having a z-score greater than 1
a study on cooking times at high altitudes, with 90% of the data falling above the population mean
a study on the average length of hiking trails in all state parks, with 50% of the data falling below the population mean
a study on crosswalk wait times with 95% of the data falling within 1 standard deviation of the population mean
a study of employees’ annual number of vacation days, with a large standard deviation about the mean
a study with a significantly smaller than expected standard deviation about the sample mean