Porosity is the volume of space between pores of sediment particles that a liquid could fill.  Thus, it is a measure of how much space is available to store a liquid such as water or oil.  It is in such pore space between grains of sediment that ground water and oil and other liquids reside.

Permeability is a measure of how easily a liquid can move through the sediment or rock.

Consider the diagram below showing BB's in one beaker and larger marbles in another, analogous to a fine-sand sediment (or sandstone) and a coarser pebble sediment (or conglomerate).
 

• In which would the porosity be highest (or would they be the same)?

• In which would the permeability be highest (or would they be the same)?

Porosity is equal to the volume of pore space divided by the total volume (pore space plus particle volume).  In the beaker example, total volume is simply equal to the volume filled by the BB's or marbles.  Thus, you can measure the porosity by measuring how much water it takes to fill up the pore space and dividing it by the total volume the BB's or marbles take up.

Permeability is proportional to rate of flow (volume of water divided by time) times length it travels divided by the cross-sectional area of flow.  Thus, a relative measure of permeability can be determined by measuring how fast a chosen volume of water passes through a tube of constant length and diameter containing either BB's or marbles.  The shorter time corresponds to higher permeability.

 
ANSWERS:  Both have the same porosity.  The larger particles have a higher permeability.
 

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