= VEL ( x - M) 2 . P(x) ] or as the equivalent form given in Formula 5-4. 5-1 Basic Skills and Concepts Statistical Literacy and Critical Thinking 1. Random Variable The accompanying table lists probabilities for the corresponding num- Number of Girls in Four bers of girls in four births. What is the random variable, what are its possible values, and are its Births values numerical ? Number of 2. Discrete or Continuous? Is the random variable given in the accompanying table discrete Girls x P(x) or continuous? Explain. 0 0.063 0.250 3. Probability Distribution For the accompanying table, is the sum of the values of P(x) 2 0.375 equal to 1, as required for a probability distribution? Does the table describe a probability 3 0.250 distribution ? 4 0.063 4. Significant For 100 births, P(exactly 56 girls) = 0.0390 and P(56 or more girls) = 0.136. Is 56 girls in 100 births a significantly high number of girls? Which probability is relevant to answering that question? Identifying Discrete and Continuous Random Variables. In Exercises 5 and 6, refer to the given values, then identify which of the following is most appropriate: discrete ran- dom variable, continuous random variable, or not a random variable. 5. a. Exact weights of the next 100 babies born in the United States b. Responses to the survey question "Which political party do you prefer?" c. Numbers of spins of roulette wheels required to get the number 7 d. Exact foot lengths of humans e. Shoe sizes (such as 8 or 81/2) of humans 6. a. Grades (A, B, C, D, F) earned in statistics classes b. Heights of students in statistics classes c. Numbers of students in statistics classes d. Eye colors of statistics students e. Numbers of times statistics students must toss a coin before getting heads