Biology SL
Biology SL
4
Chapters
553
Notes
Theme A - Unity & Diversity
Theme A - Unity & Diversity
Theme B - Form & Function
Theme B - Form & Function
Theme C - Interaction &  Interdependence
Theme C - Interaction & Interdependence
Theme D - Continuity & Change
Theme D - Continuity & Change
IB Resources
Theme D - Continuity & Change
Biology SL
Biology SL

Theme D - Continuity & Change

Unlock Chi-Squared Test Secrets In Genetics!

Word Count Emoji
604 words
Reading Time Emoji
4 mins read
Updated at Emoji
Last edited on 14th Jun 2024

Table of content

What's Cooking? 🍳

Ever wondered how we know if a genetic cross experiment fits Mendelian ratios? It's like trying to guess the secret recipe of a dish just by tasting it. This is where chi-squared tests come to the rescue!

The Core Stuff - Hypotheses 🤔

In a chi-squared test, you have

  • H0 (Null Hypothesis): Everything is as expected; no surprises! It's like your mom telling you to clean your room, and lo and behold, it's already clean.

    🌍 Real-world example: In a genetics test, if you're expecting a 3:1 ratio, this hypothesis says, "Yep, it'll be 3:1."

  • H1 (Alternative Hypothesis): Something fishy is going on; the results are not as expected. This would be like finding a sock in your soup 🧦🍲.

    🌍 Real-world example: In the same genetics test, this hypothesis says, "Nope, it's not gonna be 3:1. Something else is up!"

The Chi-Squared Method 👩‍🔬

  • State Hypotheses: Write down your H0 and H1.
  • Create Contingency Table: It's like a bingo card but for your observed data.
  • Calculate Expected Proportions: Use the good ol' Mendelian ratios like 9:3:3:1 to figure out what you should expect.
  • Degrees of Freedom: Sounds like a rock band, but it's just the number of categories minus 1. (4 - 1) = 3 🎸
  • Critical Region: Use a chi-squared table and find the value that corresponds to your degrees of freedom. Think of this as the tipping point for your hypothesis.
  • Do the Math: Plug your observed and expected numbers into the chi-squared equation
  • χ= Σ(obs − exp)/ exp
  • Final Verdict: Compare your chi-squared value to the critical region. If it's lower, H0 stays. If higher, H0 goes out the window 🪟.

🌍 Real-world example: Bateson in 1901 tested chicken feather and comb traits. He found out that they fit the expected 9:3:3:1 ratio! The genes were indeed unlinked, just like your Wi-Fi when it goes off at crucial times.

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IB Resources
Theme D - Continuity & Change
Biology SL
Biology SL

Theme D - Continuity & Change

Unlock Chi-Squared Test Secrets In Genetics!

Word Count Emoji
604 words
Reading Time Emoji
4 mins read
Updated at Emoji
Last edited on 14th Jun 2024

Table of content

What's Cooking? 🍳

Ever wondered how we know if a genetic cross experiment fits Mendelian ratios? It's like trying to guess the secret recipe of a dish just by tasting it. This is where chi-squared tests come to the rescue!

The Core Stuff - Hypotheses 🤔

In a chi-squared test, you have

  • H0 (Null Hypothesis): Everything is as expected; no surprises! It's like your mom telling you to clean your room, and lo and behold, it's already clean.

    🌍 Real-world example: In a genetics test, if you're expecting a 3:1 ratio, this hypothesis says, "Yep, it'll be 3:1."

  • H1 (Alternative Hypothesis): Something fishy is going on; the results are not as expected. This would be like finding a sock in your soup 🧦🍲.

    🌍 Real-world example: In the same genetics test, this hypothesis says, "Nope, it's not gonna be 3:1. Something else is up!"

The Chi-Squared Method 👩‍🔬

  • State Hypotheses: Write down your H0 and H1.
  • Create Contingency Table: It's like a bingo card but for your observed data.
  • Calculate Expected Proportions: Use the good ol' Mendelian ratios like 9:3:3:1 to figure out what you should expect.
  • Degrees of Freedom: Sounds like a rock band, but it's just the number of categories minus 1. (4 - 1) = 3 🎸
  • Critical Region: Use a chi-squared table and find the value that corresponds to your degrees of freedom. Think of this as the tipping point for your hypothesis.
  • Do the Math: Plug your observed and expected numbers into the chi-squared equation
  • χ= Σ(obs − exp)/ exp
  • Final Verdict: Compare your chi-squared value to the critical region. If it's lower, H0 stays. If higher, H0 goes out the window 🪟.

🌍 Real-world example: Bateson in 1901 tested chicken feather and comb traits. He found out that they fit the expected 9:3:3:1 ratio! The genes were indeed unlinked, just like your Wi-Fi when it goes off at crucial times.

Unlock the Full Content! File Is Locked Emoji

Dive deeper and gain exclusive access to premium files of Biology SL. Subscribe now and get closer to that 45 🌟