Question

A noted psychic was tested for extrasensory perception. The psychic was presented with 200 cards face down and asked to determine if each card were one of five symbols: a star, a cross, a circle, a square, or three wavy lines. The psychic was correct in 50 cases. Let p represent the probability that the psychic correctly identifies the symbol on the card in a random trial. Assume the 200 trials can be treated as a simple random sample from the population of all guesses the psychic would make in his lifetime. Based on the results, what is a 95% confidence interval for p? (Note: Use the large-sample confidence interval.)

a. 0.25+/-0.060

b. 0.25+/-0.004

c. 0.25+/-0.05

d. 0.25+/-0.055

Answer 1