Listening Section 3: Multiple Choice & Matching: Question 4

Transcript-based practice (no audio).

Dr. Nakamura: So, talk me through the design for the seedling study before you start growing anything. You're comparing red and blue LED light, is that right? Ben: Yes, we're growing bean seedlings under red LEDs in one group and blue LEDs in another, and measuring stem height after two weeks. Dr. Nakamura: How many seedlings per group? Sofia: We were planning five per group, to keep things manageable. Dr. Nakamura: Five's quite low for a plant study. A single unusually tall or short seedling could skew your average a lot at that size. I'd push that up to at least fifteen per group if you can manage the space. Ben: We can probably manage fifteen if we use the smaller trays instead of the large pots. Sofia: Agreed, fifteen it is then, using the smaller trays. Dr. Nakamura: Good. Now, what about a control group, are you including seedlings under ordinary white light, or just comparing red against blue directly? Ben: We hadn't planned a white-light group, actually, just red versus blue. Dr. Nakamura: I'd add one. Without a white-light baseline, you can say red grew taller than blue, but you can't say whether either colour sped growth up or slowed it down compared with normal conditions, and reviewers will ask that. Sofia: That's a good point, we'll add a third group under standard white light as a baseline. Dr. Nakamura: What about watering, will that be standardised across groups? Ben: We were going to water each tray "as needed," checking the soil by eye. Sofia: I actually think we should measure a fixed volume per tray on a set schedule instead of judging it by eye. Otherwise watering becomes a second variable we're not controlling, on top of the light colour. Ben: Good call, fixed volume and schedule for everyone, then, not "as needed." Dr. Nakamura: Agreed, that removes an obvious confound. Last question. Where will the trays be positioned in the growth room? Sofia: We were going to place the red group nearer the door and the blue group at the back, just because that's where the two light rigs already are. Dr. Nakamura: That worries me slightly. The area near the door tends to be a couple of degrees cooler here, so you'd have colour and temperature varying together. I'd rotate the trays' positions partway through the two weeks, or better, move both rigs to sit side by side away from the door. Ben: Moving both rigs away from the door sounds more reliable than rotating partway through, since we won't disturb the seedlings. Sofia: Agreed, let's reposition both rigs side by side, away from the door, rather than rotating them.

Choose the correct letter, A, B or C.

1. How many seedlings per group does the final design use? A. Five B. Fifteen C. Twenty-five

2. What additional group does Dr. Nakamura recommend adding? A. A group grown in complete darkness B. A group grown under standard white light C. A group grown under green LED light

3. Why does Dr. Nakamura want a white-light baseline included? A. To show whether red or blue light speeds up or slows down growth compared with normal conditions B. To reduce the total cost of the LED equipment C. Because the funding body requires a control group by policy

4. How will watering be handled in the final design? A. Each tray watered "as needed," judged by eye B. A fixed volume of water given to each tray on a set schedule C. Seedlings watered only once, at the start of the experiment

5. Why does Sofia want watering standardised? A. To save time during the two-week study B. To avoid watering becoming an uncontrolled second variable alongside light colour C. Because the seedlings need less water under artificial light

6. How will the light rigs be arranged in the final design? A. Red group near the door, blue group at the back, as originally set up B. Trays rotated partway through the two weeks C. Both rigs repositioned side by side, away from the door