AtlasFoundations · start here
Reading the symbols (Σ, x̄, √, ², subscripts, ≥)
- Fractions, proportions, percentages and rounding
- Reading the symbols (Σ, x̄, √, ², subscripts, ≥)
Fig. 1
Five pore diameters from a micro-CT slice of a 3D-printed PCL bone scaffold (µm)
Σ = 1,550 µm over n = 5 pores.
Five pores on a micro-CT slice of the printed scaffold measure 310, 290, 330, 300 and 320 µm.
(add them all up): 310 + 290 + 330 + 300 + 320 = 1,550 µm.
The little numbers are name tags: just means pore 3, which is 330 µm.
300 means ‘300 or more’, so a pore of exactly 300 µm counts: 4 of 5 pores are ≥ 300 µm (310, 330, 300, 320).
(times itself): pore 3 and pore 4 are 30 µm apart, and 30² = 30 × 30 = 900. (undo a square): √900 = 30, back where we started.
- Σxᵢ (add them all up)
- 1,550 µm
- Pores ≥ 300 µm
- 4 of 5
- Gap squared
- 900
Explorable Prose · First look
Level 1 · First look · Foundations (ext)
Recognise each symbol as shorthand for a word or an action you already know.
Read the course's formulas aloud (Σ, x̄, √, ², subscripts, ≥ and the Greek letters) and evaluate them on a small data set.
ext A Foundations primer: written for beginners, not from the slides.
Symbols as shorthand (the step you are on)
Like '&' for 'and', Σ means 'add them all up' and ² means 'times itself'.
Σ (add them all up): the five pores make 1,550 µm. Drag pore 1 (310 µm) and the total follows.