Let X equal the yield of alfalfa in tons per acre per year. Assume that X is N(1.5, 0.09). It is hoped that a new fertilizer will increase the average yield. We shall test the null hypothesisH0: μ = 1.5 against the alternative hypothesis H1:μ > 1.5. Assume that the variance continues to equal σ2 = 0.09 with the new fertilizer. Using is such that α = K(1.5) = 0.05 and K(1.7) = 0.95.
Module #18-‐ Basic concepts of sensation and perception Sunday, February 28, 2016 5:55 PM - Heather Sellersc 'urious mix of "perfect vision" and face blindness: the distinction between sensation and perception ○ Sensation: the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment (sensory receptors detect information→nervous system transmits the information to her brain) [normal] ○ Perception: the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events [almost normal] ○ Bottom -‐up processing: analysis that begins with the sensory receptors and works up to the brain's integration of sensory information [build up from smallest pieces of sensory info/detect lines, angels, colors…] ○ Top-‐down processing: constructs perceptions from the sensory input by drawing on our experience and expectations [perception that's driven by perception/ the brain applies what you know/expected -‐-‐ perception by content/your brain add meanings] - Transduction: the process of converting one form of energy into another that our brain can use § Eg. In sensation, the transforming of stimulus energies (sights, sounds, smells…) into neural impulses our brain can interpret ○ Three basic steps to all our sensory systems § Receive sensory stimulation (specialized receptor cells) § Transform that stimulation into neural impulses § Deliver the neural information to our brain ○ Psychophysics: studies the relationships between the physical energy we can detect and its effects on our psychological experiences - Thresholds ○ Absolute thresholds: the minimum stimulus energy needed to detect a particular stimulus (eg. Light, sound, pressure, taste…) 50% of the time [the point where sth. Becomes noticeable to our sense-‐s-‐-‐anything less than this goes unnoticed] ○ For weak stimulus (or signal, such as hearing-‐test tone): signal detection theory § A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) [no single absolute threshold and the detection depends partly on a person's experience, expectations, motivation, and alertness]/[why people respond differently to the same stimuli, and why the same person's reactions vary as circumstances change] ○ Subliminal: stimuli you cannot detect 50 percent of the time for conscious awareness (below your absolute threshold) ○ Priming: the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response § Much of our information processing occurs automatically, out of sight, off the radar screen of our conscious mind. ○ Difference thresholds (just noticeable difference: jnd): the minimum difference a person can detect between any two stimuli half the time [the stimulus becomes detectable to us, how do we recognize if the stimulus changes] § It can increase with the size of the stimulus § Weber's law (Ernst Weber): the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage(rather than a constant screen of our conscious mind. ○ Difference thresholds (just noticeable difference: jnd): the minimum difference a person can detect between any two stimuli half the time [the stimulus becomes detectable to us, how do we recognize if the stimulus changes] § It can increase with the size of the stimulus § Weber's law (Ernst Weber): the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage(rather than a constant amount) □ Ex. Lights: 8%, weights: 2%, tones: 0.3% - Subliminal Persuasion ○ Acknowledge/ influence people in certain way (powerful) - Sensory adaptation: diminished sensitivity as a consequence of constant stimulation ○ Benefit: freedom to focus on informative changes in our environment without being distracted by background chatter ○ We perceived the world not exactly as it is, but as it is useful for us to perceived it. ○ It allows us to focus on changing stimuli - Perceptual Set: a mental predisposition to perceive one thing and not another, affects (top-‐down) what we hear, taste, feel and see ○ What determine our perceptual set -‐the preexisting schemas (influence how we apply top-‐down processing to interpret ambiguous sensations) - Context Effects ○ The context creates an expectation that, top down, influences our perception - Motivation and Emotion ○ Influence perceptions (top-‐down) and color our social perceptions ○ Perceptual bias