Pit vipers (including rattlesnakes) have a pit organ located halfway between their eyes and nostrils. These organs detect the body heat of unlucky warm-blooded prey (mammals), but the snakes also use the pit organ to detect cooler spots in the environment to help in their thermoregulation. Researchers determined that western diamondback rattlesnakes had on average a 73% chance of moving into the right half of a Y-maze that was cooled to 30°C, instead of the left half which was at 40°C (Krochmal et al. 2004). Was this pattern a preference for the right side of the maze (that just happened to be cooled), or was it a direct response to the difference in heat? To test this, five snakes were put into the same maze several times individually, and the percentage of trials in which they turned right was recorded when both sides were heated to 40°C. The average of the percentages for the five snakes was 47%, and the standard deviation was 13%.

a. Is there a preference for the right side of the maze when the temperature is equalized? Test the null hypothesis that the mean percentage of right turns is 50% in this population. Assume that the distribution of scores was normal.

b. Can you think of a way to design the experiment to test effects of temperature so that side preferences, if present, do not affect the

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