Question 1: A researcher wants to determine the likelihood of randomly selecting a participant with a specific trait from a group of 200 people, of which 50 have the trait. What is the probability of selecting a person with the trait? Express your answer as a fraction and as a percentage.

Answer: Fraction: 50/200 or 1/4; Percentage: 25%

Question 2: In an experiment, there are 120 students, 30 of whom are left-handed. What is the probability that a randomly chosen student is right-handed? Show your working.

Answer: Total students = 120; Left-handed = 30; Right-handed = 120 - 30 = 90; Probability = 90/120 = 3/4 or 75%

Question 3: Explain what is meant by the term 'probability' in the context of psychological research.

Answer: Probability refers to the likelihood or chance that a particular event will occur, often expressed as a fraction, decimal, or percentage.

Question 4: A bag contains 10 blue balls and 15 red balls. If a ball is drawn at random, what is the probability of drawing a blue ball? Write your answer as a decimal rounded to two decimal places.

Answer: Probability = 10/25 = 0.4

Question 5: Describe a scenario where understanding probability could help in designing an ethical psychological study.

Answer: Understanding probability helps researchers assess the chances of chance findings, ensuring they do not wrongly attribute effects to variables when they could be due to randomness, thus maintaining ethical standards of accuracy and honesty.

Question 6: A survey predicts that 60% of people prefer a new mental health app. If 150 people are surveyed, how many are expected to prefer the app? Show your working.

Answer: Expected number = 60% of 150 = 0.6 × 150 = 90 people

Question 7: In a class of 40 students, 10 students have completed a psychology course. What is the probability that a student chosen at random has not completed the course? Express your answer as a fraction.

Answer: Probability = 30/40 = 3/4

Question 8: Sketch a simple diagram representing the probability of flipping a fair coin and getting heads. Label the key parts of your diagram.

Answer: A rectangle divided into two equal parts; one labeled 'Heads' and the other 'Tails'. The 'Heads' section should be shaded or marked to show 1/2 probability, and the same for 'Tails'.

Question 9: A research study involves selecting participants from a population where 20% have a specific condition. If 50 participants are randomly selected, how many are expected to have the condition? Show your working.

Answer: Expected number = 20% of 50 = 0.2 × 50 = 10 participants

Question 10: Identify and explain two factors that can affect the accuracy of probability calculations in psychological research.

Answer: Factors include sampling bias, which can skew the results if the sample is not representative, and small sample sizes, which can lead to unreliable estimates of probability due to higher variability.