Warm-up Discussion What are the important “steps” in developing and analyzing scientific investigations? Is the process linear (meaning one step always leads to the next in the same order)? If not, explain why.

Agenda Warm-up Brainstorm: characteristics of good experiments Special notes on hypotheses (including null hypotheses) Design an experiment to investigate the response of isopods to environmental factors Bring bugs by Friday!! All procedures, raw data, and analysis should be written in your lab notebook! Revisit characteristics of good experiments Group activity: evaluating and critiquing experiments

Characteristics of Good Experiments

Hypotheses Best to use “if-then” form Indicates IN THE HYPOTHESIS what your independent and dependent variables will be (what you’ll change and what you’ll measure) Examples: Poor: I think the color green is more soothing than the color red. Doesn’t tell you enough about the experimental design! What are you measuring? Better: If rats are soothed by green more than red, then rats in a green chamber will have lower heart rates and respiratory rates than rats in a red chamber.

Hypotheses Fix these! Poor: I think cats like tuna more than they like chicken. Poor: I think my dog pees more on trees that other dogs have marked than on fresh trees.

Null Hypotheses Basically says that there will be no significant correlation/preference/difference/effect in your outcomes Examples: Hypothesis: if cats prefer tuna over chicken, then cats will eat the tuna meal more often than the chicken meal when they are given both options. Null: if cats have no preference of tuna over chicken, then they will eat both meals with equal frequency when given both options. (or cats will have no preference between tuna and chicken)

Null Hypotheses You Try! Hypothesis: If a white Chrysler 200 and black Chrysler 200 are left in the blazing Texas sun for 9 hours, then the white Chrysler 200 will have a lower interior temperature than the black Chrysler 200. Null:

Null Hypotheses You Try! Hypothesis: If bacteria grow more in sweaty versus dry environments, then more bacteria will be found on a sweaty sock than on a dry sock. Null:

Null Hypotheses You Try! Hypothesis: If Oxyclean is a more effective stain-fighter than Shout, then a grass-stained t-shirt washed with Oxyclean will be cleaner than a grass-stained t-shirt washed with Shout. Null:

Null Hypotheses Why bother with a null hypothesis? You can’t really “prove” anything in science If you can statistically reject your null hypothesis, you’re saying there is not “no difference” which is very similar to saying that there IS a difference Example AbbrHyp: Cats prefer tuna over chicken NullHyp: Cats eat tuna and chicken in equal frequencies I can never prove unequivocally that cats prefer tuna, but I can disprove that they have no preference which supports the idea that they prefer tuna

Design an experiment to investigate the response of isopods to environmental factors Isopod Behavior (or The Roly-poly Lab!) Objectives: Observe various aspects of a terrestrial isopod Conduct experiments examining the responses of isopods to various environmental factors Design and conduct an investigation of animal behavior

Isopod Behavior Today: Design the Lab Note any important background information that will help you form a question about the isopod’s response to the environment Form a question Form a testable hypothesis Form a null hypothesis Design an experiment that will allow you to support or reject your hypothesis and null hypothesis Identify independent and dependent variables (what will you change? What will you measure?) Determine materials: choice chamber, # pill bugs, etc Determine procedures – BE SPECIFIC! I should be able to read your procedures and do your EXACT experiment! Sketch out what data tables you’ll need THIS STUFF GOES IN YOUR LAB NOTEBOOK – DUE TOMORROW!! (you will type up a nice, pretty lab report later) Tomorrow: Do the Lab (gather data, begin analysis, etc)

Factors to Investigate… FactorMaterials (suggested) Temperaturecold pack, warm pack Light lamps, flashlights, dark construction paper, aluminum foil pHlow pH (HCl), high pH (NaOH) Substrate (surface) soil, sand, sandpaper, bark, paper, cedar chips, gravel Odorammonia Foodapple, potato, fish food, lunchmeat

Revisiting Characteristics of Good Experimental Design

Critiquing Experiments In your groups, you will evaluate and critique four experiments Each student will write their OWN answers Use “if/then” format for hypothesis, but you are not required to use “if/then” for the null hypothesis Be sure that your conclusions are concise and specific – it’s never enough to say that something “changed,” you must always say HOW it changed (increased, decreased, got __ °C warmer, etc…) and do not make broad generalizations that aren’t supported by the data

Hypotheses Poor: I think the bugs will move toward the wet side of the chamber. Better: If the bugs prefer a moist environment over a dry environment, then when they are randomly placed in a choice chamber and allowed to move freely for ten minutes, more bugs will be found on the wet side of the chamber than the dry side of the chamber. Null Hypothesis: If pill bugs are randomly placed in a choice chamber and allowed to move freely for ten minutes, then they will have no preference for moist versus dry and the same number will be found on each side of the chamber.