Sketch a scatterplot showing a hypothetical statistical relationship between this variable and the number of words people speak per day. Research questions in psychology are about variables. This statistical relationship is consistent with the idea that exercising causes happiness, but it is also consistent with the idea that happiness causes exercise. Nonlinear relationships are fairly common in psychology, but measuring their strength is beyond the scope of this book. How could a researcher give all Canadian teenagers or all children with autism an equal chance of being selected for a sample? This information can also be presented in a bar graph like that in Figure 2.1, where the heights of the bars represent the group means. Interpret basic statistics and graphs used to describe statistical relationships. Occurs when the average score on one variable differs systematically across the levels of the other variable. How common is it for soldiers who have served in the Canadian Forces to develop post-traumatic stress disorder (PTSD) after returning from a deployment in a war zone? Define the concept of a variable, distinguish quantitative from categorical variables, and give examples of variables that might be of interest to psychologists. Explain the difference between a population and a sample. A is a quantity, such as height, that is typically measured by assigning a number to each individual. Correlation does not imply causation. The most effective, however, is to conduct an experiment. Although this seems like a minor change to the research design, it is extremely important. The biological perspective of psychology holds that human behaviors, thoughts and feelings are products of physiological factors. Answering such questions requires operationally defining the variable, measuring it among a sample, analyzing the results, and drawing conclusions about the population. For example, the circled point in Figure 2.2 represents a person whose stress score was 10 and who had three physical symptoms. This is called the population. Practice: Imagine that you categorize people as either introverts (quieter, shyer, more inward looking) or extraverts (louder, more outgoing, more outward looking). In this example, the line that best approximates the points is a curve—a kind of upside-down “U”—because people who get about eight hours of sleep tend to be the least depressed. What Are the Five Basic Concepts of Psychology. This is what psychologists mean when they say, “Correlation does not imply causation.” An amusing example of this comes from a 2012 study that showed a positive correlation (Pearson’s r = 0.79) between the per capita chocolate consumption of a nation and the number of Nobel prizes awarded to citizens of that nation[1]. Do people who are narcissistic tend to take more selfies? One such article is about a study showing that children who ate candy every day were more likely than other children to be arrested for a violent offence later in life. For now, however, it is easiest to think in terms of two distinct groups. There are two basic forms of statistical relationship: differences between groups and correlations between quantitative variables. Pearson’s r is a good measure only for linear relationships, in which the points are best approximated by a straight line. A probability sampling method in which each individual in the population has an equal probability of being selected for the sample. Other examples of quantitative variables include people’s level of talkativeness, how depressed they are, and the number of siblings they have. The chosen major of the students is also a variable as long as not everyone in the class has declared the same major. This is a good example of a positive relationship, in which higher scores on one variable tend to be associated with higher scores on the other. According to the cognitive perspective, behavior results from mental processes. Likewise, it cannot be because some third variable (e.g., physical health) affected both how much they exercised and what mood they were in (because, again, it was the researcher who determined how much they exercised). For each, specify whether it is quantitative or categorical. A wide variety of research questions in psychology take this form. Of course, the obvious problem with convenience sampling is that the sample might not be representative of the population. Consider, for example, a study showing that whether or not people exercise is statistically related to how happy they are—such that people who exercise are happier on average than people who do not. A quantitative variable is a quantity, such as height, that is typically measured by assigning a number to each individual. But could candy really “lead to” violence, as the headline suggests? Concepts are based on Actions: The little child probably thinks a little and forms some rudimentary … It is important, therefore, for researchers to use a representative sample—one that is similar to the population in important respects. Lastly, the sociocultural perspective sees social and cultural forces as major motivators of behavior. For example, instead of simply measuring how much people exercise, a researcher could bring people into a laboratory and randomly assign half of them to run on a treadmill for 15 minutes and the rest to sit on a couch for 15 minutes. A majority of psychologists take an eclectic approach, using components of all five concepts to understand and address different human behaviors. Similarly, the statistical relationship between exercise and happiness could mean that some third variable, such as physical health, causes both of the others. Higher scores on one variable tend to be associated with lower scores on the other variable. Does the effectiveness of psychotherapy depend on how much the patient likes the therapist? How talkative are Canadian university students? Some research questions in psychology are about one variable. One basic form of statistical relationship is a difference between the mean scores of two groups on some variable of interest. The biological perspective of psychology holds that human behaviors, thoughts and feelings are products of physiological factors. ), The Secret Science of Solving Crossword Puzzles, Racist Phrases to Remove From Your Mental Lexicon. Practice: For each of the following statistical relationships, decide whether the directionality problem is present and think of at least one plausible third variable: People who eat more lobster tend to live longer. For example, a pollster could start with a list of all the registered voters in a city (the population), randomly select 100 of them from the list (the sample), and ask those 100 whom they intended to vote for. How much time per week do school children spend online? A categorical variable is a quality, such as chosen major, and is typically measured by assigning a category label to each individual (e.g., Psychology, English, Nursing, etc.). A majority of psychologists take an eclectic approach, using components of all five concepts to understand and address different human behaviors. Understanding causal relationships is important in part because it allows us to change people’s behaviour in predictable ways. Practical Strategies for Psychological Measurement, American Psychological Association (APA) Style, Writing a Research Report in American Psychological Association (APA) Style, From the “Replicability Crisis” to Open Science Practices. For example, the fact that nations that have won more Nobel prizes tend to have higher chocolate consumption probably reflects geography in that European countries tend to have higher rates of per capita chocolate consumption and invest more in education and technology (once again, per capita) than many other countries in the world. Although researchers in psychology know that correlation does not imply causation, many journalists do not. Differences between groups are usually described by giving the mean score and standard deviation for each group.

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