Many studies have investigated the question of whether people tend to think of an odd or an even number when they are asked to think of a single-digit number (0 through 9). Combining results from several studies, Kubovy and Psotka (1976) used a sample of 1,770 people, of whom 741 thought of an even number and 1,029 thought of an odd number. Would a one-sided or a two-sided alternative hypothesis be more appropriate in this case

A one-sided hypothesis is one that asserts that a given parameter is either smaller than the null hypothesis value or larger than the value presented by the null hypothesis.

However in a two sided hypothesis, the claim is made that a given parameter is not equal to the parameter given in the null hypothesis, such that the parameter can be either larger than than or lesser than the value of the null hypothesis and still satisfy the condition of the hypothesis

Therefore, given for that for there to be a conclusion, the test should be weather the number of people that think of an odd number are equal to the number of people that think of an even number, or weather the number of people that think of an odd number are not equal to the number of people that think of an even number

Therefore, a two-sided hypothesis should be used since the claim (that the numbers are not equal) is not equal to the value of the parameter in the null hypothesis (that the numbers are equal)